[Qemu-devel] [PATCH] slirp: Remove our_addr code

[Qemu-devel] [PATCH] slirp: Remove our_addr code

[Ed Swierk]

Three problems with our_addr:

- It's determined only once when qemu starts, but the address can change
(just like the DNS configuration can).

- It's supposed to be the IP address of a host network interface, but
there's no guarantee that gethostbyname(gethostname()) actually does
that: the host might be a laptop that has only a loopback interface up,
or the hostname might be localhost.localdomain, etc.

- It's useless: aside from the CU-SeeMe protocol emulation which I
propose removing, the only other reference is in get_dns_addr(), but
can't imagine why you would want to send DNS requests to a different IP
address if you're running a DNS server on the host and resolv.conf
points to 127.0.0.1.

These problems are easily solved by removing the code.

Signed-off-by: Ed Swierk <eswierk@aristanetworks.com>

---
diff --git a/slirp/main.h b/slirp/main.h
index e87b068..8d09df9 100644
--- a/slirp/main.h
+++ b/slirp/main.h
@@ -30,7 +30,6 @@ extern char *slirp_tty;
 extern char *exec_shell;
 extern u_int curtime;
 extern fd_set *global_readfds, *global_writefds, *global_xfds;
-extern struct in_addr our_addr;
 extern struct in_addr loopback_addr;
 extern char *username;
 extern char *socket_path;
diff --git a/slirp/slirp.c b/slirp/slirp.c
index 3214c29..aead5b0 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -26,8 +26,6 @@
 #include "slirp.h"
 #include "hw/hw.h"
 
-/* host address */
-struct in_addr our_addr;
 /* host loopback address */
 struct in_addr loopback_addr;
 
@@ -129,8 +127,6 @@ int get_dns_addr(struct in_addr *pdns_addr)
         if (sscanf(buff, "nameserver%*[ \t]%256s", buff2) == 1) {
             if (!inet_aton(buff2, &tmp_addr))
                 continue;
-            if (tmp_addr.s_addr == loopback_addr.s_addr)
-                tmp_addr = our_addr;
             /* If it's the first one, set it to dns_addr */
             if (!found) {
                 *pdns_addr = tmp_addr;
@@ -164,8 +160,6 @@ int get_dns_addr(struct in_addr *pdns_addr)
 static void slirp_init_once(void)
 {
     static int initialized;
-    struct hostent *he;
-    char our_name[256];
 #ifdef _WIN32
     WSADATA Data;
 #endif
@@ -181,17 +175,6 @@ static void slirp_init_once(void)
 #endif
 
     loopback_addr.s_addr = htonl(INADDR_LOOPBACK);
-
-    /* FIXME: This address may change during runtime */
-    if (gethostname(our_name, sizeof(our_name)) == 0) {
-        he = gethostbyname(our_name);
-        if (he) {
-            our_addr = *(struct in_addr *)he->h_addr;
-        }
-    }
-    if (our_addr.s_addr == 0) {
-        our_addr = loopback_addr;
-    }
 }
 
 static void slirp_state_save(QEMUFile *f, void *opaque);

[Qemu-devel] Re: [PATCH] slirp: Remove our_addr code

[Ed Swierk]

On Thu, Jul 23, 2009 at 1:37 AM, Ed Swierk<eswierk@aristanetworks.com> wrote:
> - It's useless: aside from the CU-SeeMe protocol emulation which I
> propose removing, the only other reference is in get_dns_addr(), but
> can't imagine why you would want to send DNS requests to a different IP
> address if you're running a DNS server on the host and resolv.conf
> points to 127.0.0.1.
>
> These problems are easily solved by removing the code.

Note that VirtualBox removed this code recently as well:
http://www.virtualbox.org/ticket/1470 .

--Ed

[Qemu-devel] Re: [PATCH] slirp: Remove our_addr code

[Jan Kiszka]

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Ed Swierk wrote:
> On Thu, Jul 23, 2009 at 1:37 AM, Ed Swierk<eswierk@aristanetworks.com> wrote:
>> - It's useless: aside from the CU-SeeMe protocol emulation which I
>> propose removing, the only other reference is in get_dns_addr(), but
>> can't imagine why you would want to send DNS requests to a different IP
>> address if you're running a DNS server on the host and resolv.conf
>> points to 127.0.0.1.
>>
>> These problems are easily solved by removing the code.
> 
> Note that VirtualBox removed this code recently as well:
> http://www.virtualbox.org/ticket/1470 .

While I don't consider VirtualBox as a good reference for changing QEMU
code ;), the patch has my conditional ack (depending on the CUSEEME
emulation removal).

Thanks for picking all this up!
Jan


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[Qemu-devel] [PATCH] slirp: Remove our_addr code

[Ed Swierk]

Three problems with our_addr:

- It's determined only once when qemu starts, but the address can change
(just like the DNS configuration can).

- It's supposed to be the IP address of a host network interface, but
there's no guarantee that gethostbyname(gethostname()) actually does
that: the host might be a laptop that has only a loopback interface up,
or the hostname might be localhost.localdomain, etc.

- It's useless: get_dns_addr() calls it, but can't imagine why you would
want to send DNS requests to a different IP address if you're running a
DNS server on the host and resolv.conf points to 127.0.0.1.

These problems are easily solved by removing the code.

Signed-off-by: Ed Swierk <eswierk@aristanetworks.com>

---
diff --git a/slirp/main.h b/slirp/main.h
index e87b068..8d09df9 100644
--- a/slirp/main.h
+++ b/slirp/main.h
@@ -30,7 +30,6 @@ extern char *slirp_tty;
 extern char *exec_shell;
 extern u_int curtime;
 extern fd_set *global_readfds, *global_writefds, *global_xfds;
-extern struct in_addr our_addr;
 extern struct in_addr loopback_addr;
 extern char *username;
 extern char *socket_path;
diff --git a/slirp/slirp.c b/slirp/slirp.c
index 987aad9..7e3945e 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -27,8 +27,6 @@
 #include "slirp.h"
 #include "hw/hw.h"
 
-/* host address */
-struct in_addr our_addr;
 /* host loopback address */
 struct in_addr loopback_addr;
 
@@ -130,8 +128,6 @@ int get_dns_addr(struct in_addr *pdns_addr)
         if (sscanf(buff, "nameserver%*[ \t]%256s", buff2) == 1) {
             if (!inet_aton(buff2, &tmp_addr))
                 continue;
-            if (tmp_addr.s_addr == loopback_addr.s_addr)
-                tmp_addr = our_addr;
             /* If it's the first one, set it to dns_addr */
             if (!found) {
                 *pdns_addr = tmp_addr;
@@ -165,8 +161,6 @@ int get_dns_addr(struct in_addr *pdns_addr)
 static void slirp_init_once(void)
 {
     static int initialized;
-    struct hostent *he;
-    char our_name[256];
 #ifdef _WIN32
     WSADATA Data;
 #endif
@@ -182,17 +176,6 @@ static void slirp_init_once(void)
 #endif
 
     loopback_addr.s_addr = htonl(INADDR_LOOPBACK);
-
-    /* FIXME: This address may change during runtime */
-    if (gethostname(our_name, sizeof(our_name)) == 0) {
-        he = gethostbyname(our_name);
-        if (he) {
-            our_addr = *(struct in_addr *)he->h_addr;
-        }
-    }
-    if (our_addr.s_addr == 0) {
-        our_addr = loopback_addr;
-    }
 }
 
 static void slirp_state_save(QEMUFile *f, void *opaque);