path: root/util/oslib-win32.c
diff options
authorSebastian Ottlik <>2013-10-02 12:23:12 +0200
committerStefan Weil <>2013-10-02 19:20:31 +0200
commit606600a176c981addcfedb0698f13fd0f2f4446e (patch)
treeb9ddd847daa6eeb96e3de8b754a8ea14ab434214 /util/oslib-win32.c
parenta684f3cf9b9b9c3cb82be87aafc463de8974610c (diff)
util: add socket_set_fast_reuse function which will replace setting SO_REUSEADDR
If a socket is closed it remains in TIME_WAIT state for some time. On operating systems using BSD sockets the endpoint of the socket may not be reused while in this state unless SO_REUSEADDR was set on the socket. On windows on the other hand the default behaviour is to allow reuse (i.e. identical to SO_REUSEADDR on other operating systems) and setting SO_REUSEADDR on a socket allows it to be bound to a endpoint even if the endpoint is already used by another socket independently of the other sockets state. This can even result in undefined behaviour. Many sockets used by QEMU should not block the use of their endpoint after being closed while they are still in TIME_WAIT state. Currently QEMU sets SO_REUSEADDR for such sockets, which can lead to problems on Windows. This patch introduces the function socket_set_fast_reuse that should be used instead of setting SO_REUSEADDR when fast socket reuse is desired and behaves correctly on all operating systems. As a failure of this function can only be caused by bad QEMU internal errors, an assertion handles these situations. The return value is still passed on, to minimize changes in client code and prevent unused variable warnings if NDEBUG is defined. Signed-off-by: Sebastian Ottlik <> Reviewed-by: Eric Blake <> Signed-off-by: Stefan Weil <>
Diffstat (limited to 'util/oslib-win32.c')
1 files changed, 10 insertions, 0 deletions
diff --git a/util/oslib-win32.c b/util/oslib-win32.c
index 983b7a2..776ccfa 100644
--- a/util/oslib-win32.c
+++ b/util/oslib-win32.c
@@ -124,6 +124,16 @@ void qemu_set_nonblock(int fd)
+int socket_set_fast_reuse(int fd)
+ /* Enabling the reuse of an endpoint that was used by a socket still in
+ * TIME_WAIT state is usually performed by setting SO_REUSEADDR. On Windows
+ * fast reuse is the default and SO_REUSEADDR does strange things. So we
+ * don't have to do anything here. More info can be found at:
+ * */
+ return 0;
int inet_aton(const char *cp, struct in_addr *ia)
uint32_t addr = inet_addr(cp);
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