Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[David Miller]

From: Jeff Chua <jeff.chua.linux@gmail.com>
Date: Thu, 5 Feb 2009 22:41:52 +0800

[ netdev CC:'d, please always do this for networking stuff ]

> The following commit breaks "rlogin". Symptom is the terminal just
> hangs before login to the remote machine. No error, just the cursor
> never come back. "~." or type "exit" will exit from remote session.
> Only happens "sometimes". Happens more often if you try many times.
> 
> I've reverted the commit, and rlogin works now.
 ...
> commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8
> Author: Herbert Xu <herbert@gondor.apana.org.au>
> Date:   Thu Dec 25 17:12:58 2008 -0800
> 
>     tcp: Always set urgent pointer if it's beyond snd_nxt

Oh well, what is running on each side of the rlogin attempt?

Herbert, please help Jeff try to track down the cause of this.
If we can't figure it out soon I'll have to revert.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Linus Torvalds]

On Thu, 5 Feb 2009, David Miller wrote:
> 
> Herbert, please help Jeff try to track down the cause of this.
> If we can't figure it out soon I'll have to revert.

Why is there even any discussion?

URG is broken as a concept, no sane/modern use case exists. It's totally 
uninteresting _except_ as a "legacy binary" issue, so

 - there's no point in trying to "improve" it.

 - even just a whiff of "breaks legacy app" just says "revert it".

No?

		Linus

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[David Miller]

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 5 Feb 2009 15:32:20 -0800 (PST)

> On Thu, 5 Feb 2009, David Miller wrote:
> > 
> > Herbert, please help Jeff try to track down the cause of this.
> > If we can't figure it out soon I'll have to revert.
> 
> Why is there even any discussion?
> 
> URG is broken as a concept, no sane/modern use case exists. It's totally 
> uninteresting _except_ as a "legacy binary" issue, so
> 
>  - there's no point in trying to "improve" it.
> 
>  - even just a whiff of "breaks legacy app" just says "revert it".
> 
> No?

Sure, and we can put the change back in if we ever figure out what the
problem was.

This change is in 2.6.28 too, so I'll revert and queue the revert up
for -stable as well.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Thu, Feb 05, 2009 at 03:32:20PM -0800, Linus Torvalds wrote:
> 
> Why is there even any discussion?
> 
> URG is broken as a concept, no sane/modern use case exists. It's totally 
> uninteresting _except_ as a "legacy binary" issue, so
> 
>  - there's no point in trying to "improve" it.
> 
>  - even just a whiff of "breaks legacy app" just says "revert it".
> 
> No?

It's more complex than that.  We'll need to do exactly this in
the future in order to support IPv6 jumbograms because that's
the only way to use the 16-bit urgent pointer in a packet bigger
than 64K.  It's also what RFC2675 (http://tools.ietf.org/html/rfc2675,
section 5.2) prescribes.

IPv6 jumbograms are absolutely required if we ever want to move
beyond 10Gb/s Ethernet.

But as we're still struggling with 10Gb/s Ethernet, I'm fine with
a revert for now while we look for a fix for rlogin.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Jeff Chua]

[-- Attachment #1: Type: text/plain, Size: 1242 bytes --]

On Fri, Feb 6, 2009 at 7:29 AM, David Miller <davem@davemloft.net> wrote:
> [ netdev CC:'d, please always do this for networking stuff ]

Will do.

> Oh well, what is running on each side of the rlogin attempt?

Nothing at all. Just a pure "rlogin remotehost" trying to get a login
prompt. Nothing inside .profile.

On Fri, Feb 6, 2009 at 11:10 AM, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> Could you please try a strace on both sides, with and without
> this patch applied?

Attached are two strace. t1.good is a good rlogin run. t4.bad is bad
rlogin run where nothing is displayed but typing "~-." gets back to
the host.

With strace, it takes a bit more try to get it to hang. In fact, this
bug was quite to trigger and I've been having this problem on-and-off
since December, and but it was intermittent and didn't think it was a
kernel problem until serious chasing. Some network switches "mask" out
the problem, and some direct connect always has this problem. Some
servers occurred very frequent, some seldom.


On Fri, Feb 6, 2009 at 7:32 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>  - even just a whiff of "breaks legacy app" just says "revert it".

I agree reverting is the right thing here.


Thanks,
Jeff.

[-- Attachment #2: t1.good --]
[-- Type: application/octet-stream, Size: 14898 bytes --]

execve("/usr/bin/rlogin", ["rlogin", "ju"], [/* 72 vars */]) = 0
brk(0)                                  = 0x9c20000
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef7000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49475, ...}) = 0
old_mmap(NULL, 49475, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7eea000
close(3)                                = 0
open("/lib/libcrypt.so.1", O_RDONLY)    = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0000\7\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=38528, ...}) = 0
old_mmap(NULL, 201052, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7eb8000
old_mmap(0xb7ec1000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8000) = 0xb7ec1000
old_mmap(0xb7ec3000, 155996, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7ec3000
close(3)                                = 0
open("/lib/libutil.so.1", O_RDONLY)     = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@\n\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=9868, ...}) = 0
old_mmap(NULL, 12432, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7eb4000
old_mmap(0xb7eb6000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0xb7eb6000
close(3)                                = 0
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0 f\1\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1299568, ...}) = 0
old_mmap(NULL, 1283696, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d7a000
old_mmap(0xb7eae000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x134000) = 0xb7eae000
old_mmap(0xb7eb1000, 9840, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7eb1000
close(3)                                = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7d79000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7d798d0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xb7eae000, 8192, PROT_READ)   = 0
mprotect(0xb7eb6000, 4096, PROT_READ)   = 0
mprotect(0xb7ec1000, 4096, PROT_READ)   = 0
mprotect(0xb7f15000, 4096, PROT_READ)   = 0
munmap(0xb7eea000, 49475)               = 0
getuid32()                              = 0
brk(0)                                  = 0x9c20000
brk(0x9c41000)                          = 0x9c41000
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/nsswitch.conf", O_RDONLY)    = 3
fstat64(3, {st_mode=S_IFREG|0700, st_size=1307, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef6000
read(3, "#\n# /etc/nsswitch.conf\n#\n# An ex"..., 4096) = 1307
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7ef6000, 4096)                = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49475, ...}) = 0
old_mmap(NULL, 49475, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7eea000
close(3)                                = 0
open("/lib/libnss_files.so.2", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\340\30"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=38708, ...}) = 0
old_mmap(NULL, 41624, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d6e000
old_mmap(0xb7d77000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8000) = 0xb7d77000
close(3)                                = 0
mprotect(0xb7d77000, 4096, PROT_READ)   = 0
munmap(0xb7eea000, 49475)               = 0
open("/etc/passwd", O_RDONLY|0x80000)   = 3
fcntl64(3, F_GETFD)                     = 0x1 (flags FD_CLOEXEC)
fstat64(3, {st_mode=S_IFREG|0644, st_size=3779, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef6000
read(3, "root:bt2L4qrBrz2II:0:0:SuperUser"..., 4096) = 3779
close(3)                                = 0
munmap(0xb7ef6000, 4096)                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/services", O_RDONLY|0x80000) = 3
fstat64(3, {st_mode=S_IFREG|0755, st_size=7524, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef6000
read(3, "# /etc/services:\n# $Id: services"..., 4096) = 4096
close(3)                                = 0
munmap(0xb7ef6000, 4096)                = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, TIOCGWINSZ, {ws_row=55, ws_col=80, ws_xpixel=564, ws_ypixel=719}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGPIPE, {0x80494c0, [PIPE], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [USR1 URG], [], 8) = 0
getpid()                                = 13745
socket(PF_NETLINK, SOCK_RAW, 0)         = 3
bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
getsockname(3, {sa_family=AF_NETLINK, pid=13745, groups=00000000}, [12]) = 0
time(NULL)                              = 1233897551
sendto(3, "\24\0\0\0\26\0\1\3O\310\213I\0\0\0\0\0\0\0\0", 20, 0, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000}, msg_iov(1)=[{"0\0\0\0\24\0\2\0O\310\213I\2615\0\0\2\10\200\376\1\0\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 288
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000}, msg_iov(1)=[{"\24\0\0\0\3\0\2\0O\310\213I\2615\0\0\0\0\0\0\1\0\0\0\10"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 20
close(3)                                = 0
open("/etc/resolv.conf", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
old_mmap(NULL, 65536, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7d5e000
read(3, "domain corp.fedex.com\nnameserver"..., 65536) = 118
read(3, "", 65536)                      = 0
close(3)                                = 0
munmap(0xb7d5e000, 65536)               = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/host.conf", O_RDONLY)        = 3
fstat64(3, {st_mode=S_IFREG|0744, st_size=93, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef6000
read(3, "#order bind, hosts\norder hosts, "..., 4096) = 93
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7ef6000, 4096)                = 0
open("/etc/hosts", O_RDONLY|0x80000)    = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=96, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef6000
read(3, "# localhost ...\n127.0.0.1\tlocalh"..., 4096) = 96
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7ef6000, 4096)                = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49475, ...}) = 0
old_mmap(NULL, 49475, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7eea000
close(3)                                = 0
open("/lib/libnss_dns.so.2", O_RDONLY)  = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\300\v\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=18000, ...}) = 0
old_mmap(NULL, 20616, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d68000
old_mmap(0xb7d6c000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3000) = 0xb7d6c000
close(3)                                = 0
open("/lib/libresolv.so.2", O_RDONLY)   = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@!\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=59580, ...}) = 0
old_mmap(NULL, 71876, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d56000
old_mmap(0xb7d64000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xd000) = 0xb7d64000
old_mmap(0xb7d66000, 6340, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7d66000
close(3)                                = 0
mprotect(0xb7d64000, 4096, PROT_READ)   = 0
mprotect(0xb7d6c000, 4096, PROT_READ)   = 0
munmap(0xb7eea000, 49475)               = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
connect(3, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(3, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1233897552, 77763}, NULL) = 0
poll([{fd=3, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(3, "_\367\1\0\0\1\0\0\0\0\0\0\2ju\4corp\5fedex\3com\0\0"..., 35, MSG_NOSIGNAL) = 35
poll([{fd=3, events=POLLIN, revents=POLLIN}], 1, 5000) = 1
ioctl(3, FIONREAD, [109])               = 0
recvfrom(3, "_\367\205\200\0\1\0\2\0\1\0\1\2ju\4corp\5fedex\3com\0\0"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, [16]) = 109
close(3)                                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
ioctl(3, SIOCGIFCONF, {0 -> 160, NULL}) = 0
ioctl(3, SIOCGIFCONF, {160, {{"lo", {AF_INET, inet_addr("127.0.0.1")}}, {"lo:3", {AF_INET, inet_addr("192.168.243.1")}}, {"dummy0", {AF_INET, inet_addr("192.168.243.88")}}, {"vmnet1", {AF_INET, inet_addr("192.168.243.1")}}, {"eth0", {AF_INET, inet_addr("192.168.249.139")}}}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="lo", ifr_netmask={AF_INET, inet_addr("255.0.0.0")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="lo:3", ifr_netmask={AF_INET, inet_addr("255.255.255.255")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="dummy0", ifr_netmask={AF_INET, inet_addr("255.255.255.255")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="vmnet1", ifr_netmask={AF_INET, inet_addr("255.255.255.0")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="eth0", ifr_netmask={AF_INET, inet_addr("255.255.248.0")}}) = 0
close(3)                                = 0
open("/etc/hosts", O_RDONLY|0x80000)    = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=96, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef6000
read(3, "# localhost ...\n127.0.0.1\tlocalh"..., 4096) = 96
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7ef6000, 4096)                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
connect(3, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(3, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1233897552, 293794}, NULL) = 0
poll([{fd=3, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(3, "G\212\1\0\0\1\0\0\0\0\0\0\003118\003243\003168\003192\7"..., 46, MSG_NOSIGNAL) = 46
poll([{fd=3, events=POLLIN, revents=POLLIN}], 1, 5000) = 1
ioctl(3, FIONREAD, [118])               = 0
recvfrom(3, "G\212\205\200\0\1\0\1\0\1\0\1\003118\003243\003168\003"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, [16]) = 118
close(3)                                = 0
rt_sigprocmask(SIG_BLOCK, [URG], [USR1 URG], 8) = 0
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
bind(3, {sa_family=AF_INET, sin_port=htons(1023), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
fcntl64(3, F_SETOWN, 13745)             = 0
connect(3, {sa_family=AF_INET, sin_port=htons(513), sin_addr=inet_addr("192.168.243.118")}, 16) = 0
write(3, "\0", 1)                       = 1
writev(3, [{"root\0", 5}, {"root\0", 5}, {"xterm/38400\0", 12}], 3) = 22
read(3, "\0", 1)                        = 1
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [USR1 URG], 8) = 0
setsockopt(3, SOL_IP, IP_TOS, [16], 4)  = 0
setuid32(0)                             = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGINT, {SIG_IGN}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [HUP], [USR1 URG], 8) = 0
rt_sigaction(SIGHUP, {0x8048bdc, [HUP], SA_RESTART}, {SIG_IGN}, 8) = 0
rt_sigaction(SIGHUP, {SIG_IGN}, {0x8048bdc, [HUP], SA_RESTART}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [HUP USR1 URG], 8) = 0
rt_sigprocmask(SIG_BLOCK, [QUIT], [USR1 URG], 8) = 0
rt_sigaction(SIGQUIT, {0x8048bdc, [QUIT], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [QUIT USR1 URG], 8) = 0
rt_sigaction(SIGCHLD, {0x8049f20, [CHLD], SA_RESTART}, {SIG_DFL}, 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7d79918) = 13746
rt_sigaction(SIGURG, {0x80491d0, [URG], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigaction(SIGUSR1, {0x8048de0, [USR1], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], [USR1 URG], 8) = 0
--- SIGURG (Urgent I/O condition) @ 0 (0) ---
kill(13746, SIGURG)                     = 0
sigreturn()                             = ? (mask now [])
read(0, "~", 1)                         = 1
read(0, ".", 1)                         = 1
write(1, "~.\r\n", 4)                   = 4
write(2, "rlogin: closed connection.\r\n", 28) = 28
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost -isig -icanon -echo ...}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost -isig -icanon -echo ...}) = 0
ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGCHLD, {SIG_DFL}, {0x8049f20, [CHLD], SA_RESTART}, 8) = 0
kill(13746, SIGKILL)                    = 0
wait4(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGKILL}], 0, NULL) = 13746
--- SIGCHLD (Child exited) @ 0 (0) ---
exit_group(0)                           = ?

[-- Attachment #3: t4.bad --]
[-- Type: application/octet-stream, Size: 15008 bytes --]

execve("/usr/bin/rlogin", ["rlogin", "ju"], [/* 72 vars */]) = 0
brk(0)                                  = 0x9aed000
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f1f000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49475, ...}) = 0
old_mmap(NULL, 49475, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7f12000
close(3)                                = 0
open("/lib/libcrypt.so.1", O_RDONLY)    = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0000\7\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=38528, ...}) = 0
old_mmap(NULL, 201052, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7ee0000
old_mmap(0xb7ee9000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8000) = 0xb7ee9000
old_mmap(0xb7eeb000, 155996, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7eeb000
close(3)                                = 0
open("/lib/libutil.so.1", O_RDONLY)     = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@\n\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=9868, ...}) = 0
old_mmap(NULL, 12432, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7edc000
old_mmap(0xb7ede000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0xb7ede000
close(3)                                = 0
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0 f\1\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1299568, ...}) = 0
old_mmap(NULL, 1283696, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7da2000
old_mmap(0xb7ed6000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x134000) = 0xb7ed6000
old_mmap(0xb7ed9000, 9840, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7ed9000
close(3)                                = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7da1000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7da18d0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xb7ed6000, 8192, PROT_READ)   = 0
mprotect(0xb7ede000, 4096, PROT_READ)   = 0
mprotect(0xb7ee9000, 4096, PROT_READ)   = 0
mprotect(0xb7f3d000, 4096, PROT_READ)   = 0
munmap(0xb7f12000, 49475)               = 0
getuid32()                              = 0
brk(0)                                  = 0x9aed000
brk(0x9b0e000)                          = 0x9b0e000
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/nsswitch.conf", O_RDONLY)    = 3
fstat64(3, {st_mode=S_IFREG|0700, st_size=1307, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f1e000
read(3, "#\n# /etc/nsswitch.conf\n#\n# An ex"..., 4096) = 1307
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7f1e000, 4096)                = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49475, ...}) = 0
old_mmap(NULL, 49475, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7f12000
close(3)                                = 0
open("/lib/libnss_files.so.2", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\340\30"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=38708, ...}) = 0
old_mmap(NULL, 41624, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d96000
old_mmap(0xb7d9f000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8000) = 0xb7d9f000
close(3)                                = 0
mprotect(0xb7d9f000, 4096, PROT_READ)   = 0
munmap(0xb7f12000, 49475)               = 0
open("/etc/passwd", O_RDONLY|0x80000)   = 3
fcntl64(3, F_GETFD)                     = 0x1 (flags FD_CLOEXEC)
fstat64(3, {st_mode=S_IFREG|0644, st_size=3779, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f1e000
read(3, "root:bt2L4qrBrz2II:0:0:SuperUser"..., 4096) = 3779
close(3)                                = 0
munmap(0xb7f1e000, 4096)                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/services", O_RDONLY|0x80000) = 3
fstat64(3, {st_mode=S_IFREG|0755, st_size=7524, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f1e000
read(3, "# /etc/services:\n# $Id: services"..., 4096) = 4096
close(3)                                = 0
munmap(0xb7f1e000, 4096)                = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, TIOCGWINSZ, {ws_row=55, ws_col=80, ws_xpixel=564, ws_ypixel=719}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGPIPE, {0x80494c0, [PIPE], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [USR1 URG], [], 8) = 0
getpid()                                = 13726
socket(PF_NETLINK, SOCK_RAW, 0)         = 3
bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
getsockname(3, {sa_family=AF_NETLINK, pid=13726, groups=00000000}, [12]) = 0
time(NULL)                              = 1233897475
sendto(3, "\24\0\0\0\26\0\1\3\3\310\213I\0\0\0\0\0\0\0\0", 20, 0, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000}, msg_iov(1)=[{"0\0\0\0\24\0\2\0\3\310\213I\2365\0\0\2\10\200\376\1\0\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 288
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000}, msg_iov(1)=[{"\24\0\0\0\3\0\2\0\3\310\213I\2365\0\0\0\0\0\0\1\0\0\0\10"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 20
close(3)                                = 0
open("/etc/resolv.conf", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=118, ...}) = 0
old_mmap(NULL, 65536, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7d86000
read(3, "domain corp.fedex.com\nnameserver"..., 65536) = 118
read(3, "", 65536)                      = 0
close(3)                                = 0
munmap(0xb7d86000, 65536)               = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/host.conf", O_RDONLY)        = 3
fstat64(3, {st_mode=S_IFREG|0744, st_size=93, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f1e000
read(3, "#order bind, hosts\norder hosts, "..., 4096) = 93
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7f1e000, 4096)                = 0
open("/etc/hosts", O_RDONLY|0x80000)    = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=96, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f1e000
read(3, "# localhost ...\n127.0.0.1\tlocalh"..., 4096) = 96
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7f1e000, 4096)                = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49475, ...}) = 0
old_mmap(NULL, 49475, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7f12000
close(3)                                = 0
open("/lib/libnss_dns.so.2", O_RDONLY)  = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\300\v\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=18000, ...}) = 0
old_mmap(NULL, 20616, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d90000
old_mmap(0xb7d94000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3000) = 0xb7d94000
close(3)                                = 0
open("/lib/libresolv.so.2", O_RDONLY)   = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@!\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=59580, ...}) = 0
old_mmap(NULL, 71876, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d7e000
old_mmap(0xb7d8c000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xd000) = 0xb7d8c000
old_mmap(0xb7d8e000, 6340, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7d8e000
close(3)                                = 0
mprotect(0xb7d8c000, 4096, PROT_READ)   = 0
mprotect(0xb7d94000, 4096, PROT_READ)   = 0
munmap(0xb7f12000, 49475)               = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
connect(3, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(3, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1233897475, 633762}, NULL) = 0
poll([{fd=3, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(3, "\306t\1\0\0\1\0\0\0\0\0\0\2ju\4corp\5fedex\3com\0\0"..., 35, MSG_NOSIGNAL) = 35
poll([{fd=3, events=POLLIN, revents=POLLIN}], 1, 5000) = 1
ioctl(3, FIONREAD, [109])               = 0
recvfrom(3, "\306t\205\200\0\1\0\2\0\1\0\1\2ju\4corp\5fedex\3com\0\0"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, [16]) = 109
close(3)                                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
ioctl(3, SIOCGIFCONF, {0 -> 160, NULL}) = 0
ioctl(3, SIOCGIFCONF, {160, {{"lo", {AF_INET, inet_addr("127.0.0.1")}}, {"lo:3", {AF_INET, inet_addr("192.168.243.1")}}, {"dummy0", {AF_INET, inet_addr("192.168.243.88")}}, {"vmnet1", {AF_INET, inet_addr("192.168.243.1")}}, {"eth0", {AF_INET, inet_addr("192.168.249.139")}}}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="lo", ifr_netmask={AF_INET, inet_addr("255.0.0.0")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="lo:3", ifr_netmask={AF_INET, inet_addr("255.255.255.255")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="dummy0", ifr_netmask={AF_INET, inet_addr("255.255.255.255")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="vmnet1", ifr_netmask={AF_INET, inet_addr("255.255.255.0")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="eth0", ifr_netmask={AF_INET, inet_addr("255.255.248.0")}}) = 0
close(3)                                = 0
open("/etc/hosts", O_RDONLY|0x80000)    = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=96, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f1e000
read(3, "# localhost ...\n127.0.0.1\tlocalh"..., 4096) = 96
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7f1e000, 4096)                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
connect(3, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(3, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1233897475, 698466}, NULL) = 0
poll([{fd=3, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(3, "#\364\1\0\0\1\0\0\0\0\0\0\003118\003243\003168\003192\7"..., 46, MSG_NOSIGNAL) = 46
poll([{fd=3, events=POLLIN, revents=POLLIN}], 1, 5000) = 1
ioctl(3, FIONREAD, [118])               = 0
recvfrom(3, "#\364\205\200\0\1\0\1\0\1\0\1\003118\003243\003168\003"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, [16]) = 118
close(3)                                = 0
rt_sigprocmask(SIG_BLOCK, [URG], [USR1 URG], 8) = 0
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
bind(3, {sa_family=AF_INET, sin_port=htons(1023), sin_addr=inet_addr("0.0.0.0")}, 16) = -1 EADDRINUSE (Address already in use)
bind(3, {sa_family=AF_INET, sin_port=htons(1022), sin_addr=inet_addr("0.0.0.0")}, 16) = -1 EADDRINUSE (Address already in use)
bind(3, {sa_family=AF_INET, sin_port=htons(1021), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
fcntl64(3, F_SETOWN, 13726)             = 0
connect(3, {sa_family=AF_INET, sin_port=htons(513), sin_addr=inet_addr("192.168.243.118")}, 16) = 0
write(3, "\0", 1)                       = 1
writev(3, [{"root\0", 5}, {"root\0", 5}, {"xterm/38400\0", 12}], 3) = 22
read(3, "\0", 1)                        = 1
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [USR1 URG], 8) = 0
setsockopt(3, SOL_IP, IP_TOS, [16], 4)  = 0
setuid32(0)                             = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGINT, {SIG_IGN}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [HUP], [USR1 URG], 8) = 0
rt_sigaction(SIGHUP, {0x8048bdc, [HUP], SA_RESTART}, {SIG_IGN}, 8) = 0
rt_sigaction(SIGHUP, {SIG_IGN}, {0x8048bdc, [HUP], SA_RESTART}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [HUP USR1 URG], 8) = 0
rt_sigprocmask(SIG_BLOCK, [QUIT], [USR1 URG], 8) = 0
rt_sigaction(SIGQUIT, {0x8048bdc, [QUIT], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [QUIT USR1 URG], 8) = 0
rt_sigaction(SIGCHLD, {0x8049f20, [CHLD], SA_RESTART}, {SIG_DFL}, 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7da1918) = 13728
rt_sigaction(SIGURG, {0x80491d0, [URG], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigaction(SIGUSR1, {0x8048de0, [USR1], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], [USR1 URG], 8) = 0
read(0, "~", 1)                         = 1
read(0, ".", 1)                         = 1
write(1, "~.\r\n", 4)                   = 4
write(2, "rlogin: closed connection.\r\n", 28) = 28
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost -isig -icanon -echo ...}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost -isig -icanon -echo ...}) = 0
ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGCHLD, {SIG_DFL}, {0x8049f20, [CHLD], SA_RESTART}, 8) = 0
kill(13728, SIGKILL)                    = 0
wait4(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGKILL}], 0, NULL) = 13728
--- SIGCHLD (Child exited) @ 0 (0) ---
exit_group(0)                           = ?

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Fri, Feb 06, 2009 at 01:39:19PM +0800, Jeff Chua wrote:
> 
> Attached are two strace. t1.good is a good rlogin run. t4.bad is bad
> rlogin run where nothing is displayed but typing "~-." gets back to
> the host.

You traced the side receiving the urgent pointer.  This has
nothing to do with the patch since it only changes sending
behaviour.

Did you change the kernel on the other side during these tests?

If reverting the patch on the other side does fix the problem
for you, please do the two straces there.

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Jeff Chua]

[-- Attachment #1: Type: text/plain, Size: 1103 bytes --]

On Fri, Feb 6, 2009 at 1:45 PM, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> On Fri, Feb 06, 2009 at 01:39:19PM +0800, Jeff Chua wrote:
>>
>> Attached are two strace. t1.good is a good rlogin run. t4.bad is bad
>> rlogin run where nothing is displayed but typing "~-." gets back to
>> the host.
>
> You traced the side receiving the urgent pointer.  This has
> nothing to do with the patch since it only changes sending
> behaviour.

The problem is the "remote" side that's frozen. The "local" side can
be on any kernel version and it won't have any effect. The runs that I
did was for one good run with "strace -o t1.good rlogin ju" that has
the bad kernel and a second one with "strace -o t4.bad rlogin ju" that
just hang.

> Did you change the kernel on the other side during these tests?

No. Was hoping that the traces would show where it hang for the good
and bad trace.

> If reverting the patch on the other side does fix the problem
> for you, please do the two straces there.

Sorry, forgot to send the good trace run for the patched remote side.
Here's attached. t5.good.

Thanks,
Jeff.

[-- Attachment #2: t5.good --]
[-- Type: application/octet-stream, Size: 14894 bytes --]

execve("/usr/bin/rlogin", ["rlogin", "ju"], [/* 72 vars */]) = 0
brk(0)                                  = 0x9ddf000
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7eff000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49556, ...}) = 0
old_mmap(NULL, 49556, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7ef2000
close(3)                                = 0
open("/lib/libcrypt.so.1", O_RDONLY)    = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0000\7\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=38528, ...}) = 0
old_mmap(NULL, 201052, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7ec0000
old_mmap(0xb7ec9000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8000) = 0xb7ec9000
old_mmap(0xb7ecb000, 155996, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7ecb000
close(3)                                = 0
open("/lib/libutil.so.1", O_RDONLY)     = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@\n\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=9868, ...}) = 0
old_mmap(NULL, 12432, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7ebc000
old_mmap(0xb7ebe000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0xb7ebe000
close(3)                                = 0
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0 f\1\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1299568, ...}) = 0
old_mmap(NULL, 1283696, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d82000
old_mmap(0xb7eb6000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x134000) = 0xb7eb6000
old_mmap(0xb7eb9000, 9840, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7eb9000
close(3)                                = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7d81000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7d818d0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xb7eb6000, 8192, PROT_READ)   = 0
mprotect(0xb7ebe000, 4096, PROT_READ)   = 0
mprotect(0xb7ec9000, 4096, PROT_READ)   = 0
mprotect(0xb7f1d000, 4096, PROT_READ)   = 0
munmap(0xb7ef2000, 49556)               = 0
getuid32()                              = 0
brk(0)                                  = 0x9ddf000
brk(0x9e00000)                          = 0x9e00000
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/nsswitch.conf", O_RDONLY)    = 3
fstat64(3, {st_mode=S_IFREG|0700, st_size=1307, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7efe000
read(3, "#\n# /etc/nsswitch.conf\n#\n# An ex"..., 4096) = 1307
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7efe000, 4096)                = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49556, ...}) = 0
old_mmap(NULL, 49556, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7ef2000
close(3)                                = 0
open("/lib/libnss_files.so.2", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\340\30"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=38708, ...}) = 0
old_mmap(NULL, 41624, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d76000
old_mmap(0xb7d7f000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x8000) = 0xb7d7f000
close(3)                                = 0
mprotect(0xb7d7f000, 4096, PROT_READ)   = 0
munmap(0xb7ef2000, 49556)               = 0
open("/etc/passwd", O_RDONLY|0x80000)   = 3
fcntl64(3, F_GETFD)                     = 0x1 (flags FD_CLOEXEC)
fstat64(3, {st_mode=S_IFREG|0644, st_size=3779, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7efe000
read(3, "root:bt2L4qrBrz2II:0:0:SuperUser"..., 4096) = 3779
close(3)                                = 0
munmap(0xb7efe000, 4096)                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/services", O_RDONLY|0x80000) = 3
fstat64(3, {st_mode=S_IFREG|0755, st_size=7524, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7efe000
read(3, "# /etc/services:\n# $Id: services"..., 4096) = 4096
close(3)                                = 0
munmap(0xb7efe000, 4096)                = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, TIOCGWINSZ, {ws_row=55, ws_col=80, ws_xpixel=564, ws_ypixel=719}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGPIPE, {0x80494c0, [PIPE], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [USR1 URG], [], 8) = 0
getpid()                                = 6432
socket(PF_NETLINK, SOCK_RAW, 0)         = 3
bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
getsockname(3, {sa_family=AF_NETLINK, pid=6432, groups=00000000}, [12]) = 0
time(NULL)                              = 1233919044
sendto(3, "\24\0\0\0\26\0\1\3D\34\214I\0\0\0\0\0\0\0\0", 20, 0, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000}, msg_iov(1)=[{"0\0\0\0\24\0\2\0D\34\214I \31\0\0\2\10\200\376\1\0\0\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 288
recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000}, msg_iov(1)=[{"\24\0\0\0\3\0\2\0D\34\214I \31\0\0\0\0\0\0\1\0\0\0\10\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 20
close(3)                                = 0
open("/etc/resolv.conf", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=95, ...}) = 0
old_mmap(NULL, 65536, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7d66000
read(3, "domain corp.fedex.com\nnameserver"..., 65536) = 95
read(3, "", 65536)                      = 0
close(3)                                = 0
munmap(0xb7d66000, 65536)               = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
socket(PF_FILE, SOCK_STREAM, 0)         = 3
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
connect(3, {sa_family=AF_FILE, path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory)
close(3)                                = 0
open("/etc/host.conf", O_RDONLY)        = 3
fstat64(3, {st_mode=S_IFREG|0744, st_size=93, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7efe000
read(3, "#order bind, hosts\norder hosts, "..., 4096) = 93
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7efe000, 4096)                = 0
open("/etc/hosts", O_RDONLY|0x80000)    = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=96, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7efe000
read(3, "# localhost ...\n127.0.0.1\tlocalh"..., 4096) = 96
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7efe000, 4096)                = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=49556, ...}) = 0
old_mmap(NULL, 49556, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7ef2000
close(3)                                = 0
open("/lib/libnss_dns.so.2", O_RDONLY)  = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\300\v\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=18000, ...}) = 0
old_mmap(NULL, 20616, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d70000
old_mmap(0xb7d74000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3000) = 0xb7d74000
close(3)                                = 0
open("/lib/libresolv.so.2", O_RDONLY)   = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@!\0\000"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=59580, ...}) = 0
old_mmap(NULL, 71876, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7d5e000
old_mmap(0xb7d6c000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xd000) = 0xb7d6c000
old_mmap(0xb7d6e000, 6340, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7d6e000
close(3)                                = 0
mprotect(0xb7d6c000, 4096, PROT_READ)   = 0
mprotect(0xb7d74000, 4096, PROT_READ)   = 0
munmap(0xb7ef2000, 49556)               = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
connect(3, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(3, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1233919044, 748150}, NULL) = 0
poll([{fd=3, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(3, "w\306\1\0\0\1\0\0\0\0\0\0\2ju\4corp\5fedex\3com\0\0"..., 35, MSG_NOSIGNAL) = 35
poll([{fd=3, events=POLLIN, revents=POLLIN}], 1, 5000) = 1
ioctl(3, FIONREAD, [109])               = 0
recvfrom(3, "w\306\205\200\0\1\0\2\0\1\0\1\2ju\4corp\5fedex\3com\0\0"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, [16]) = 109
close(3)                                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
ioctl(3, SIOCGIFCONF, {0 -> 160, NULL}) = 0
ioctl(3, SIOCGIFCONF, {160, {{"lo", {AF_INET, inet_addr("127.0.0.1")}}, {"lo:3", {AF_INET, inet_addr("192.168.243.1")}}, {"dummy0", {AF_INET, inet_addr("192.168.243.88")}}, {"eth0", {AF_INET, inet_addr("155.161.225.157")}}, {"vmnet1", {AF_INET, inet_addr("192.168.243.1")}}}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="lo", ifr_netmask={AF_INET, inet_addr("255.0.0.0")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="lo:3", ifr_netmask={AF_INET, inet_addr("255.255.255.255")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="dummy0", ifr_netmask={AF_INET, inet_addr("255.255.255.255")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="eth0", ifr_netmask={AF_INET, inet_addr("255.255.252.0")}}) = 0
ioctl(3, SIOCGIFNETMASK, {ifr_name="vmnet1", ifr_netmask={AF_INET, inet_addr("255.255.255.0")}}) = 0
close(3)                                = 0
open("/etc/hosts", O_RDONLY|0x80000)    = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=96, ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7efe000
read(3, "# localhost ...\n127.0.0.1\tlocalh"..., 4096) = 96
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7efe000, 4096)                = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
connect(3, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0
fcntl64(3, F_GETFL)                     = 0x2 (flags O_RDWR)
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK)  = 0
gettimeofday({1233919044, 964183}, NULL) = 0
poll([{fd=3, events=POLLOUT, revents=POLLOUT}], 1, 0) = 1
send(3, "\227\345\1\0\0\1\0\0\0\0\0\0\003118\003243\003168\0031"..., 46, MSG_NOSIGNAL) = 46
poll([{fd=3, events=POLLIN, revents=POLLIN}], 1, 5000) = 1
ioctl(3, FIONREAD, [118])               = 0
recvfrom(3, "\227\345\205\200\0\1\0\1\0\1\0\1\003118\003243\003168\003"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, [16]) = 118
close(3)                                = 0
rt_sigprocmask(SIG_BLOCK, [URG], [USR1 URG], 8) = 0
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
bind(3, {sa_family=AF_INET, sin_port=htons(1023), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
fcntl64(3, F_SETOWN, 6432)              = 0
connect(3, {sa_family=AF_INET, sin_port=htons(513), sin_addr=inet_addr("192.168.243.118")}, 16) = 0
write(3, "\0", 1)                       = 1
writev(3, [{"root\0", 5}, {"root\0", 5}, {"xterm/38400\0", 12}], 3) = 22
read(3, "\0", 1)                        = 1
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [USR1 URG], 8) = 0
setsockopt(3, SOL_IP, IP_TOS, [16], 4)  = 0
setuid32(0)                             = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGINT, {SIG_IGN}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [HUP], [USR1 URG], 8) = 0
rt_sigaction(SIGHUP, {0x8048bdc, [HUP], SA_RESTART}, {SIG_IGN}, 8) = 0
rt_sigaction(SIGHUP, {SIG_IGN}, {0x8048bdc, [HUP], SA_RESTART}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [HUP USR1 URG], 8) = 0
rt_sigprocmask(SIG_BLOCK, [QUIT], [USR1 URG], 8) = 0
rt_sigaction(SIGQUIT, {0x8048bdc, [QUIT], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [QUIT USR1 URG], 8) = 0
rt_sigaction(SIGCHLD, {0x8049f20, [CHLD], SA_RESTART}, {SIG_DFL}, 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7d81918) = 6433
rt_sigaction(SIGURG, {0x80491d0, [URG], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigaction(SIGUSR1, {0x8048de0, [USR1], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], [USR1 URG], 8) = 0
--- SIGURG (Urgent I/O condition) @ 0 (0) ---
kill(6433, SIGURG)                      = 0
sigreturn()                             = ? (mask now [])
read(0, "~", 1)                         = 1
read(0, ".", 1)                         = 1
write(1, "~.\r\n", 4)                   = 4
write(2, "rlogin: closed connection.\r\n", 28) = 28
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost -isig -icanon -echo ...}) = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost -isig -icanon -echo ...}) = 0
ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGCHLD, {SIG_DFL}, {0x8049f20, [CHLD], SA_RESTART}, 8) = 0
kill(6433, SIGKILL)                     = 0
wait4(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGKILL}], 0, NULL) = 6433
--- SIGCHLD (Child exited) @ 0 (0) ---
exit_group(0)                           = ?

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Fri, Feb 06, 2009 at 07:35:50PM +0800, Jeff Chua wrote:
>
> > Did you change the kernel on the other side during these tests?
> 
> No. Was hoping that the traces would show where it hang for the good
> and bad trace.

Then the problem isn't my patch at all.  My patch only affects
the side sending the urgent data, according to your straces, rlogin
is only receiving urgent data, not sending it.  So the patch cannot
have an affect.

> > If reverting the patch on the other side does fix the problem
> > for you, please do the two straces there.
> 
> Sorry, forgot to send the good trace run for the patched remote side.
> Here's attached. t5.good.

No you're still stracing rlogin, which in this case is the receiver
of the urgent data.  Please strace the sending side, which would be
presumably be rlogind in this case.

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[David Miller]

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Mon, 9 Feb 2009 16:58:48 +1100

> On Fri, Feb 06, 2009 at 07:35:50PM +0800, Jeff Chua wrote:
> >
> > > Did you change the kernel on the other side during these tests?
> > 
> > No. Was hoping that the traces would show where it hang for the good
> > and bad trace.
> 
> Then the problem isn't my patch at all.  My patch only affects
> the side sending the urgent data, according to your straces, rlogin
> is only receiving urgent data, not sending it.  So the patch cannot
> have an affect.

Hmmm... let's figure out exactly what's going on here.

I would expect to see the URG packets from rlogin not rlogind, from
things like hitting Ctrl-C etc.

On the other hand, I can't imagine what the server, rlogind, would be
sending URGs out for.

So I would say that it is more likely to be rlogin sending the
URG packets.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Sun, Feb 08, 2009 at 10:03:57PM -0800, David Miller wrote:
> 
> I would expect to see the URG packets from rlogin not rlogind, from
> things like hitting Ctrl-C etc.

That's what I thought too, however, the strace says otherwise:

connect(3, {sa_family=AF_INET, sin_port=htons(513), sin_addr=inet_addr("192.168.243.118")}, 16) = 0
write(3, "\0", 1)                       = 1
writev(3, [{"root\0", 5}, {"root\0", 5}, {"xterm/38400\0", 12}], 3) = 22
read(3, "\0", 1)                        = 1
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [USR1 URG], 8) = 0
setsockopt(3, SOL_IP, IP_TOS, [16], 4)  = 0
setuid32(0)                             = 0
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
rt_sigaction(SIGINT, {SIG_IGN}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [HUP], [USR1 URG], 8) = 0
rt_sigaction(SIGHUP, {0x8048bdc, [HUP], SA_RESTART}, {SIG_IGN}, 8) = 0
rt_sigaction(SIGHUP, {SIG_IGN}, {0x8048bdc, [HUP], SA_RESTART}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [HUP USR1 URG], 8) = 0
rt_sigprocmask(SIG_BLOCK, [QUIT], [USR1 URG], 8) = 0
rt_sigaction(SIGQUIT, {0x8048bdc, [QUIT], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [USR1 URG], [QUIT USR1 URG], 8) = 0
rt_sigaction(SIGCHLD, {0x8049f20, [CHLD], SA_RESTART}, {SIG_DFL}, 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7d81918) = 6433
rt_sigaction(SIGURG, {0x80491d0, [URG], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigaction(SIGUSR1, {0x8048de0, [USR1], SA_RESTART}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], [USR1 URG], 8) = 0
--- SIGURG (Urgent I/O condition) @ 0 (0) ---
kill(6433, SIGURG)                      = 0

FD 3 is the TCP socket.  As you can see, the only operations done
were write/writev/read/setsockopt.  None of these can enter urgent
mode for sending, so that's how I concluded that my patch should
have zero effect on this side.

Note also that we got an SIGURG, which indicates that we received
urgent data.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Ilpo Järvinen]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 3815 bytes --]

On Mon, 9 Feb 2009, Herbert Xu wrote:

> On Sun, Feb 08, 2009 at 10:03:57PM -0800, David Miller wrote:
> > 
> > I would expect to see the URG packets from rlogin not rlogind, from
> > things like hitting Ctrl-C etc.
> 
> That's what I thought too, however, the strace says otherwise:
> 
> connect(3, {sa_family=AF_INET, sin_port=htons(513), sin_addr=inet_addr("192.168.243.118")}, 16) = 0
> write(3, "\0", 1)                       = 1
> writev(3, [{"root\0", 5}, {"root\0", 5}, {"xterm/38400\0", 12}], 3) = 22
> read(3, "\0", 1)                        = 1
> rt_sigprocmask(SIG_SETMASK, [USR1 URG], [USR1 URG], 8) = 0
> setsockopt(3, SOL_IP, IP_TOS, [16], 4)  = 0
> setuid32(0)                             = 0
> ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
> rt_sigaction(SIGINT, {SIG_IGN}, {SIG_DFL}, 8) = 0
> rt_sigprocmask(SIG_BLOCK, [HUP], [USR1 URG], 8) = 0
> rt_sigaction(SIGHUP, {0x8048bdc, [HUP], SA_RESTART}, {SIG_IGN}, 8) = 0
> rt_sigaction(SIGHUP, {SIG_IGN}, {0x8048bdc, [HUP], SA_RESTART}, 8) = 0
> rt_sigprocmask(SIG_SETMASK, [USR1 URG], [HUP USR1 URG], 8) = 0
> rt_sigprocmask(SIG_BLOCK, [QUIT], [USR1 URG], 8) = 0
> rt_sigaction(SIGQUIT, {0x8048bdc, [QUIT], SA_RESTART}, {SIG_DFL}, 8) = 0
> rt_sigprocmask(SIG_SETMASK, [USR1 URG], [QUIT USR1 URG], 8) = 0
> rt_sigaction(SIGCHLD, {0x8049f20, [CHLD], SA_RESTART}, {SIG_DFL}, 8) = 0
> clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7d81918) = 6433
> rt_sigaction(SIGURG, {0x80491d0, [URG], SA_RESTART}, {SIG_DFL}, 8) = 0
> rt_sigaction(SIGUSR1, {0x8048de0, [USR1], SA_RESTART}, {SIG_DFL}, 8) = 0
> rt_sigprocmask(SIG_SETMASK, [], [USR1 URG], 8) = 0
> --- SIGURG (Urgent I/O condition) @ 0 (0) ---
> kill(6433, SIGURG)                      = 0
> 
> FD 3 is the TCP socket.  As you can see, the only operations done
> were write/writev/read/setsockopt.  None of these can enter urgent
> mode for sending, so that's how I concluded that my patch should
> have zero effect on this side.
> 
> Note also that we got an SIGURG, which indicates that we received
> urgent data.

Hmm, what happens if a opposite dir ACK gets sent (it's zero sized seqno 
range will be above urgent sequence when urg is not yet acknowledged)? So 
we'll take the later branch after your change and send bogus 0xffff urg?
I think you're change might have actually broken bidir tcp completely (and 
probably window probing as well under some conditions). Congraz, two flies 
with a single stroke :-). You would have needed an additional check that 
the tcb->seq is below urg...

...Below is a patch but Jeff might need to revert the revert first if
he tests with the latest Linus' tree.


-- 
 i.

[PATCH] tcp: check that we're still < urg instead of sending a bogus one

Opposite dir ACK with zero sized seqno range can go into the
later condition once urg is in the outstanding window not
yet acknowledge (we're still in urg mode but seqno we sent in
the ack won't be below snd_up). Need to check that we never
advertize bogus urg for a segment which is after the snd_up.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
---
 net/ipv4/tcp_output.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 557fe16..c808d73 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -667,7 +667,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 		if (between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF)) {
 			th->urg_ptr = htons(tp->snd_up - tcb->seq);
 			th->urg = 1;
-		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
+		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt) &&
+			   before(tcb->seq, tcp->snd_up)) {
 			th->urg_ptr = 0xFFFF;
 			th->urg = 1;
 		}
-- 
1.5.6.5

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Mon, Feb 09, 2009 at 09:13:00AM +0200, Ilpo Järvinen wrote:
> 
> Hmm, what happens if a opposite dir ACK gets sent (it's zero sized seqno
> range will be above urgent sequence when urg is not yet acknowledged)? So
> we'll take the later branch after your change and send bogus 0xffff urg?
> I think you're change might have actually broken bidir tcp completely (and
> probably window probing as well under some conditions). Congraz, two flies
> with a single stroke :-). You would have needed an additional check that
> the tcb->seq is below urg...
> 
> ...Below is a patch but Jeff might need to revert the revert first if
> he tests with the latest Linus' tree.

Good point! That would definitely explain this.
 
> [PATCH] tcp: check that we're still < urg instead of sending a bogus one
> 
> Opposite dir ACK with zero sized seqno range can go into the
> later condition once urg is in the outstanding window not
> yet acknowledge (we're still in urg mode but seqno we sent in
> the ack won't be below snd_up). Need to check that we never
> advertize bogus urg for a segment which is after the snd_up.
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> ---
>  net/ipv4/tcp_output.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 557fe16..c808d73 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -667,7 +667,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
>  		if (between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF)) {
>  			th->urg_ptr = htons(tp->snd_up - tcb->seq);
>  			th->urg = 1;
> -		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
> +		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt) &&
> +			   before(tcb->seq, tcp->snd_up)) {
>  			th->urg_ptr = 0xFFFF;
>  			th->urg = 1;
>  		}

We could rewrite this as

	if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tcp->snd_up))) {
		if (before(tp->sndup, tcb->seq + 0x10000)) {
			th->urg_ptr = htons(tp->snd_up - tcb->seq);
			th->urg = 1;
		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
			th->urg_ptr = 0xFFFF;
			th->urg = 1;
		}
	}

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Mon, Feb 09, 2009 at 06:28:06PM +1100, Herbert Xu wrote:
> On Mon, Feb 09, 2009 at 09:13:00AM +0200, Ilpo Järvinen wrote:
> > 
> > Hmm, what happens if a opposite dir ACK gets sent (it's zero sized seqno
> > range will be above urgent sequence when urg is not yet acknowledged)? So
> > we'll take the later branch after your change and send bogus 0xffff urg?
> > I think you're change might have actually broken bidir tcp completely (and
> > probably window probing as well under some conditions). Congraz, two flies
> > with a single stroke :-). You would have needed an additional check that
> > the tcb->seq is below urg...
> > 
> > ...Below is a patch but Jeff might need to revert the revert first if
> > he tests with the latest Linus' tree.
> 
> Good point! That would definitely explain this.

Actually, I don't see how we can have tcp_urg_mode being true
when his strace shows no OOB data at all (it only did write
and writev).

So I'm not sure if this bug is the one causing this.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Ilpo Järvinen]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 2387 bytes --]

On Mon, 9 Feb 2009, Herbert Xu wrote:

> On Mon, Feb 09, 2009 at 09:13:00AM +0200, Ilpo Järvinen wrote:
> > 
> > Hmm, what happens if a opposite dir ACK gets sent (it's zero sized seqno
> > range will be above urgent sequence when urg is not yet acknowledged)? So
> > we'll take the later branch after your change and send bogus 0xffff urg?
> > I think you're change might have actually broken bidir tcp completely (and
> > probably window probing as well under some conditions). Congraz, two flies
> > with a single stroke :-). You would have needed an additional check that
> > the tcb->seq is below urg...
> > 
> > ...Below is a patch but Jeff might need to revert the revert first if
> > he tests with the latest Linus' tree.
> 
> Good point! That would definitely explain this.
>  
> > [PATCH] tcp: check that we're still < urg instead of sending a bogus one
> > 
> > Opposite dir ACK with zero sized seqno range can go into the
> > later condition once urg is in the outstanding window not
> > yet acknowledge (we're still in urg mode but seqno we sent in
> > the ack won't be below snd_up). Need to check that we never
> > advertize bogus urg for a segment which is after the snd_up.
> > 
> > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> > ---
> >  net/ipv4/tcp_output.c |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> > 
> > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> > index 557fe16..c808d73 100644
> > --- a/net/ipv4/tcp_output.c
> > +++ b/net/ipv4/tcp_output.c
> > @@ -667,7 +667,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
> >  		if (between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF)) {
> >  			th->urg_ptr = htons(tp->snd_up - tcb->seq);
> >  			th->urg = 1;
> > -		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
> > +		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt) &&
> > +			   before(tcb->seq, tcp->snd_up)) {
> >  			th->urg_ptr = 0xFFFF;
> >  			th->urg = 1;
> >  		}
> 
> We could rewrite this as
> 
> 	if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tcp->snd_up))) {
> 		if (before(tp->sndup, tcb->seq + 0x10000)) {
> 			th->urg_ptr = htons(tp->snd_up - tcb->seq);
> 			th->urg = 1;
> 		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
> 			th->urg_ptr = 0xFFFF;
> 			th->urg = 1;
> 		}
> 	}

Yes, that should work too except the gcc catchable typo.


-- 
 i.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Jeff Chua]

On Mon, Feb 9, 2009 at 3:13 PM, Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> wrote:
>  net/ipv4/tcp_output.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 557fe16..c808d73 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -667,7 +667,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
>                if (between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF)) {
>                        th->urg_ptr = htons(tp->snd_up - tcb->seq);
>                        th->urg = 1;
> -               } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
> +               } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt) &&
> +                          before(tcb->seq, tcp->snd_up)) {
>                        th->urg_ptr = 0xFFFF;
>                        th->urg = 1;
>                }
> --
> 1.5.6.5
>

Ilpo,

Got this error ...

  CC      net/ipv4/tcp_output.o
net/ipv4/tcp_output.c: In function 'tcp_transmit_skb':
net/ipv4/tcp_output.c:671: error: 'tcp' undeclared (first use in this function)
net/ipv4/tcp_output.c:671: error: (Each undeclared identifier is
reported only once
net/ipv4/tcp_output.c:671: error: for each function it appears in.)

> +                          before(tcb->seq, tcp->snd_up)) {

That should be "tp->snd_up" instead of "tcp->snd_up". Other than that,
the good news is I've tested your patch on top of Herbert's patch, and
it works! No more rlogin hangs!

Thanks,
Jeff.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Linus Torvalds]

On Mon, 9 Feb 2009, Herbert Xu wrote:
> 
> Then the problem isn't my patch at all.  My patch only affects
> the side sending the urgent data, according to your straces, rlogin
> is only receiving urgent data, not sending it.  So the patch cannot
> have an affect.

The trace is incolclusive about that - just look at it. It's not following 
threads/children etc, so it's missing all the relevant pieces.

Which you should have realized, Herbert, since you had the knowledge that 
your patch _DOES_ make a difference, enough to bisect to it, and enough 
to see that reverting it changes behaviour.

Why are you arguing against facts?

>From the trace:

	clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7d81918) = 6433
	rt_sigaction(SIGURG, {0x80491d0, [URG], SA_RESTART}, {SIG_DFL}, 8) = 0
	rt_sigaction(SIGUSR1, {0x8048de0, [USR1], SA_RESTART}, {SIG_DFL}, 8) = 0
	rt_sigprocmask(SIG_SETMASK, [], [USR1 URG], 8) = 0
	--- SIGURG (Urgent I/O condition) @ 0 (0) ---
	kill(6433, SIGURG)                      = 0

IOW, the trace isn't saying anything at all, because all the real work 
probably got done in that child process.

> No you're still stracing rlogin, which in this case is the receiver
> of the urgent data.  Please strace the sending side, which would be
> presumably be rlogind in this case.

Herbert, how sure are you that there is no URG data on that side?

You clearly spent _zero_ time actually looking at the trace, so...

		Linus

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Mon, Feb 09, 2009 at 07:44:56AM -0800, Linus Torvalds wrote:
>
> The trace is incolclusive about that - just look at it. It's not following 
> threads/children etc, so it's missing all the relevant pieces.
> 
> Which you should have realized, Herbert, since you had the knowledge that 
> your patch _DOES_ make a difference, enough to bisect to it, and enough 
> to see that reverting it changes behaviour.
> 
> Why are you arguing against facts?
> 
> >From the trace:
> 
> 	clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0xb7d81918) = 6433
> 	rt_sigaction(SIGURG, {0x80491d0, [URG], SA_RESTART}, {SIG_DFL}, 8) = 0
> 	rt_sigaction(SIGUSR1, {0x8048de0, [USR1], SA_RESTART}, {SIG_DFL}, 8) = 0
> 	rt_sigprocmask(SIG_SETMASK, [], [USR1 URG], 8) = 0
> 	--- SIGURG (Urgent I/O condition) @ 0 (0) ---
> 	kill(6433, SIGURG)                      = 0
> 
> IOW, the trace isn't saying anything at all, because all the real work 
> probably got done in that child process.

Ah yes, I knew the strace didn't tally with the reported behaviour,
but I'd been focusing on the SIGURG and missed the clone.  Thanks!
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Mon, Feb 09, 2009 at 03:28:09PM +0200, Ilpo Järvinen wrote:
>
> Yes, that should work too except the gcc catchable typo.

Thanks, so let's try again for net-next:

tcp: Always set urgent pointer if it's beyond snd_nxt

Our TCP stack does not set the urgent flag if the urgent pointer
does not fit in 16 bits, i.e., if it is more than 64K from the
sequence number of a packet.

This behaviour is different from the BSDs, and clearly contradicts
the purpose of urgent mode, which is to send the notification
(though not necessarily the associated data) as soon as possible.
Our current behaviour may in fact delay the urgent notification
indefinitely if the receiver window does not open up.

Simply matching BSD however may break legacy applications which
incorrectly rely on the out-of-band delivery of urgent data, and
conversely the in-band delivery of non-urgent data.

Alexey Kuznetsov suggested a safe solution of following BSD only
if the urgent pointer itself has not yet been transmitted.  This
way we guarantee that when the remote end sees the packet with
non-urgent data marked as urgent due to wrap-around we would have
advanced the urgent pointer beyond, either to the actual urgent
data or to an as-yet untransmitted packet.

The only potential downside is that applications on the remote
end may see multiple SIGURG notifications.  However, this would
occur anyway with other TCP stacks.  More importantly, the outcome
of such a duplicate notification is likely to be harmless since
the signal itself does not carry any information other than the
fact that we're in urgent mode.

Thanks to Ilpo Järvinen for fixing a critical bug in this and
Jeff Chua for reporting that bug.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index dda42f0..f5263c8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -663,10 +663,14 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 	th->urg_ptr		= 0;
 
 	/* The urg_mode check is necessary during a below snd_una win probe */
-	if (unlikely(tcp_urg_mode(tp) &&
-		     between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF))) {
-		th->urg_ptr		= htons(tp->snd_up - tcb->seq);
-		th->urg			= 1;
+	if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
+		if (before(tp->snd_up, tcb->seq + 0x10000)) {
+			th->urg_ptr = htons(tp->snd_up - tcb->seq);
+			th->urg = 1;
+		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
+			th->urg_ptr = 0xFFFF;
+			th->urg = 1;
+		}
 	}
 
 	tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location);

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Ilpo Järvinen]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 3186 bytes --]

On Sat, 21 Feb 2009, Herbert Xu wrote:

> On Mon, Feb 09, 2009 at 03:28:09PM +0200, Ilpo Järvinen wrote:
> >
> > Yes, that should work too except the gcc catchable typo.
> 
> Thanks, so let's try again for net-next:
> 
> tcp: Always set urgent pointer if it's beyond snd_nxt
> 
> Our TCP stack does not set the urgent flag if the urgent pointer
> does not fit in 16 bits, i.e., if it is more than 64K from the
> sequence number of a packet.
> 
> This behaviour is different from the BSDs, and clearly contradicts
> the purpose of urgent mode, which is to send the notification
> (though not necessarily the associated data) as soon as possible.
> Our current behaviour may in fact delay the urgent notification
> indefinitely if the receiver window does not open up.
> 
> Simply matching BSD however may break legacy applications which
> incorrectly rely on the out-of-band delivery of urgent data, and
> conversely the in-band delivery of non-urgent data.
> 
> Alexey Kuznetsov suggested a safe solution of following BSD only
> if the urgent pointer itself has not yet been transmitted.  This
> way we guarantee that when the remote end sees the packet with
> non-urgent data marked as urgent due to wrap-around we would have
> advanced the urgent pointer beyond, either to the actual urgent
> data or to an as-yet untransmitted packet.
> 
> The only potential downside is that applications on the remote
> end may see multiple SIGURG notifications.  However, this would
> occur anyway with other TCP stacks.  More importantly, the outcome
> of such a duplicate notification is likely to be harmless since
> the signal itself does not carry any information other than the
> fact that we're in urgent mode.
> 
> Thanks to Ilpo Järvinen for fixing a critical bug in this and
> Jeff Chua for reporting that bug.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index dda42f0..f5263c8 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -663,10 +663,14 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
>  	th->urg_ptr		= 0;
>  
>  	/* The urg_mode check is necessary during a below snd_una win probe */
> -	if (unlikely(tcp_urg_mode(tp) &&
> -		     between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF))) {
> -		th->urg_ptr		= htons(tp->snd_up - tcb->seq);
> -		th->urg			= 1;
> +	if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
> +		if (before(tp->snd_up, tcb->seq + 0x10000)) {
> +			th->urg_ptr = htons(tp->snd_up - tcb->seq);
> +			th->urg = 1;
> +		} else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
> +			th->urg_ptr = 0xFFFF;
> +			th->urg = 1;
> +		}
>  	}
>  
>  	tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location);

I thought this through already at the last time... so I think it really 
should work in all cases I could think of (including the below window 
probes whose existance is not very obvious before they bite back :-)):

Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>

But I mostly agree with Linus that URG is legacy that would be good
to just deprecate instead of trying to "fix" it.


-- 
 i.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[David Miller]

From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi>
Date: Sat, 21 Feb 2009 20:54:11 +0200 (EET)

> On Sat, 21 Feb 2009, Herbert Xu wrote:
> 
> > On Mon, Feb 09, 2009 at 03:28:09PM +0200, Ilpo Järvinen wrote:
> > >
> > > Yes, that should work too except the gcc catchable typo.
> > 
> > Thanks, so let's try again for net-next:
> > 
> > tcp: Always set urgent pointer if it's beyond snd_nxt
 ...
> I thought this through already at the last time... so I think it really 
> should work in all cases I could think of (including the below window 
> probes whose existance is not very obvious before they bite back :-)):
> 
> Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
> 
> But I mostly agree with Linus that URG is legacy that would be good
> to just deprecate instead of trying to "fix" it.

Sure, but I'll give Herbert one more chance :-)

Applied to net-next-2.6

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Jeff Chua]

On Sun, Feb 22, 2009 at 3:53 PM, David Miller <davem@davemloft.net> wrote:

> Sure, but I'll give Herbert one more chance :-)
>
> Applied to net-next-2.6

I see that this is already in linux-2.6.29-rc6. Tested and working fine.

Thanks,
Jeff.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Herbert Xu]

On Tue, Feb 24, 2009 at 02:40:30PM +0800, Jeff Chua wrote:
> On Sun, Feb 22, 2009 at 3:53 PM, David Miller <davem@davemloft.net> wrote:
> 
> > Sure, but I'll give Herbert one more chance :-)
> >
> > Applied to net-next-2.6
> 
> I see that this is already in linux-2.6.29-rc6. Tested and working fine.

Are you sure? It's not in my copy of rc6 :)

net-next-2.6 is for the release after the current one so the
earliest you're going to see this is in 2.6.30.

For now you'll either need to pull net-next-2.6 directly, use
linux-next, or apply the patch by hand.

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[David Miller]

From: Jeff Chua <jeff.chua.linux@gmail.com>
Date: Tue, 24 Feb 2009 14:40:30 +0800

> On Sun, Feb 22, 2009 at 3:53 PM, David Miller <davem@davemloft.net> wrote:
> 
> > Sure, but I'll give Herbert one more chance :-)
> >
> > Applied to net-next-2.6
> 
> I see that this is already in linux-2.6.29-rc6. Tested and working fine.

Actually, it isn't.

Herbert's change is in net-next-2.6 which will show up in linux-next
rather than Linus's 2.6.29-rcX tree.

Re: commit 64ff3b938ec6782e6585a83d5459b98b0c3f6eb8 breaks rlogin

[Jeff Chua]

On Tue, Feb 24, 2009 at 2:46 PM, David Miller <davem@davemloft.net> wrote:
> Actually, it isn't.
>
> Herbert's change is in net-next-2.6 which will show up in linux-next
> rather than Linus's 2.6.29-rcX tree.
>

Uh, I got it wrong. Didn't look into details. Just noticed that
tcp_output.c was changed today, so I just assume that was the one ...
which turned out to a one-liner comment removed.

Anyway, I just tested the Herbert's patch and it looks good. rlogin not hanging.

Sorry for the earlier fault report.

Thanks
Jeff.