From: Stephen Hemminger <stephen@networkplumber.org>
To: netdev@vger.kernel.org
Subject: Fw: [Bug 96381] New: TUN/TAP user API regression in 3.19, non-bloking read returns 0 when no data is available rather than EAGAIN
Date: Fri, 10 Apr 2015 13:10:59 -0700 [thread overview]
Message-ID: <20150410131059.304d579c@urahara> (raw)
Begin forwarded message:
Date: Thu, 9 Apr 2015 09:25:41 +0000
From: "bugzilla-daemon@bugzilla.kernel.org" <bugzilla-daemon@bugzilla.kernel.org>
To: "shemminger@linux-foundation.org" <shemminger@linux-foundation.org>
Subject: [Bug 96381] New: TUN/TAP user API regression in 3.19, non-bloking read returns 0 when no data is available rather than EAGAIN
https://bugzilla.kernel.org/show_bug.cgi?id=96381
Bug ID: 96381
Summary: TUN/TAP user API regression in 3.19, non-bloking read
returns 0 when no data is available rather than EAGAIN
Product: Networking
Version: 2.5
Kernel Version: 3.19.3
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: high
Priority: P1
Component: Other
Assignee: shemminger@linux-foundation.org
Reporter: ambrop7@gmail.com
Regression: No
With kernel 3.19, a read() from a TUN/TAP file descriptor in non-blocking mode
will return 0 when no data is available, rather than fail with EAGAIN. This
breaks certain applications which will interpret the 0 return value as a
zero-length packet and happily go on reading more packets.
Here's relevant parts of my application showing the change of behavior and how
the application locks up with kernel 3.19.
-- strace with 3.18 --
open("/dev/net/tun", O_RDWR) = 5
ioctl(5, TUNSETIFF, 0x7ffe24f1e620) = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 6
ioctl(6, SIOCGIFMTU, {ifr_name="tun4", ifr_mtu=1500}) = 0
close(6) = 0
fcntl(5, F_SETFL, O_RDONLY|O_NONBLOCK) = 0
epoll_ctl(3, EPOLL_CTL_ADD, 5, {0, {u32=6509592, u64=6509592}}) = 0
read(5, 0xac8010, 1500) = -1 EAGAIN (Resource temporarily
unavailable)
epoll_ctl(3, EPOLL_CTL_MOD, 5, {EPOLLIN, {u32=6509592, u64=6509592}}) = 0
-- strace with 3.19 --
open("/dev/net/tun", O_RDWR) = 5
ioctl(5, TUNSETIFF, 0x7ffea2f4d970) = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 6
ioctl(6, SIOCGIFMTU, {ifr_name="tun4", ifr_mtu=1500}) = 0
close(6) = 0
fcntl(5, F_SETFL, O_RDONLY|O_NONBLOCK) = 0
epoll_ctl(3, EPOLL_CTL_ADD, 5, {0, {u32=6509592, u64=6509592}}) = 0
read(5, "", 1500) = 0
read(5, "", 1500) = 0
read(5, "", 1500) = 0
read(5, "", 1500) = 0
read(5, "", 1500) = 0
...
--
You are receiving this mail because:
You are the assignee for the bug.
reply other threads:[~2015-04-10 20:10 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150410131059.304d579c@urahara \
--to=stephen@networkplumber.org \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox