[Qemu-devel] [PATCH RFC 2/4] net: do not set SO_REUSEADDR on Windows

[Sebastian Ottlik <ottlik@fzi.de>]

If a socket is closed it may remain in TIME_WAIT state for some time. On most
operating systems the local port of the connection or socket may not be reeused
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 may result in
undefined behaviour. Fix this issue by no setting SO_REUSEADDR on windows.

Signed-off-by: Sebastian Ottlik <ottlik@fzi.de>
---
 net/socket.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/socket.c b/net/socket.c
index e61309d..f44ebcb 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -262,12 +262,14 @@ static int net_socket_mcast_create(struct sockaddr_in *mcastaddr, struct in_addr
         return -1;
     }
 
+#ifndef _WIN32
     val = 1;
     ret = qemu_setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
     if (ret < 0) {
         perror("setsockopt(SOL_SOCKET, SO_REUSEADDR)");
         goto fail;
     }
+#endif
 
     ret = bind(fd, (struct sockaddr *)mcastaddr, sizeof(*mcastaddr));
     if (ret < 0) {
@@ -523,8 +525,10 @@ static int net_socket_listen_init(NetClientState *peer,
     qemu_set_nonblock(fd);
 
     /* allow fast reuse */
+#ifndef _WIN32
     val = 1;
     qemu_setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
+#endif
 
     ret = bind(fd, (struct sockaddr *)&saddr, sizeof(saddr));
     if (ret < 0) {
@@ -661,6 +665,7 @@ static int net_socket_udp_init(NetClientState *peer,
         perror("socket(PF_INET, SOCK_DGRAM)");
         return -1;
     }
+#ifndef _WIN32
     val = 1;
     ret = qemu_setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
                           &val, sizeof(val));
@@ -669,6 +674,7 @@ static int net_socket_udp_init(NetClientState *peer,
         closesocket(fd);
         return -1;
     }
+#endif
     ret = bind(fd, (struct sockaddr *)&laddr, sizeof(laddr));
     if (ret < 0) {
         perror("bind");
-- 
1.7.9.5