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[Qemu-devel] [PATCH] handle bind(), listen() race
From: |
Simon Rowe |
Subject: |
[Qemu-devel] [PATCH] handle bind(), listen() race |
Date: |
Tue, 26 Apr 2011 10:52:06 +0100 |
User-agent: |
KMail/1.13.3 (Linux/2.6.33.7-desktop586-2mnb; KDE/4.4.3; i686; ; ) |
Hello, we've seen a very occasional failure in the startup of qemu where the
call to inet_listen() for the VNC port fails with EADDRINUSE.
I believe there is a race condition when two qemu processes both bind to the
same port, in one the subsequent call to listen() will succeed and the other
fail. Below is a patch which appears to deal with this scenario but we would
appreciate any comments on it.
Thanks
Simon
diff -ur qemu-0.14.0-org/qemu-sockets.c qemu-0.14.0/qemu-sockets.c
--- qemu-0.14.0-org/qemu-sockets.c 2011-02-16 14:44:05.000000000 +0000
+++ qemu-0.14.0/qemu-sockets.c 2011-04-26 10:41:14.472067346 +0100
@@ -158,6 +158,7 @@
/* create socket + bind */
for (e = res; e != NULL; e = e->ai_next) {
+rebind:
getnameinfo((struct sockaddr*)e->ai_addr,e->ai_addrlen,
uaddr,INET6_ADDRSTRLEN,uport,32,
NI_NUMERICHOST | NI_NUMERICSERV);
@@ -182,7 +183,19 @@
if (sockets_debug)
fprintf(stderr,"%s: bind(%s,%s,%d): OK\n", __FUNCTION__,
inet_strfamily(e->ai_family), uaddr,
inet_getport(e));
- goto listen;
+ if (listen(slisten,1) == 0) {
+ goto listened;
+ }
+ else {
+ int err = errno;
+
+ perror("listen");
+ closesocket(slisten);
+ if (err == EADDRINUSE)
+ goto rebind;
+ freeaddrinfo(res);
+ return -1;
+ }
}
try_next = to && (inet_getport(e) <= to + port_offset);
if (!try_next || sockets_debug)
@@ -201,13 +214,7 @@
freeaddrinfo(res);
return -1;
-listen:
- if (listen(slisten,1) != 0) {
- perror("listen");
- closesocket(slisten);
- freeaddrinfo(res);
- return -1;
- }
+listened:
snprintf(uport, sizeof(uport), "%d", inet_getport(e) - port_offset);
qemu_opt_set(opts, "host", uaddr);
qemu_opt_set(opts, "port", uport);
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