slirp: Fix port comparision in slirp_remove_hostfwd

For UDP host forwardings, fport is not stable, every outgoing packet of
the redirection can modify it. Use getsockname instead to look up the
port that is actually used on the host side.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/slirp.c b/slirp.c
index f39e6ff..f3d5824 100644
--- a/slirp.c
+++ b/slirp.c
@@ -763,12 +763,16 @@ int slirp_remove_hostfwd(int is_udp, int host_port)
 {
     struct socket *so;
     struct socket *head = (is_udp ? &udb : &tcb);
-    int fport = htons(host_port);
+    struct sockaddr_in addr;
+    int port = htons(host_port);
+    socklen_t addr_len;
     int n = 0;
 
 loop_again:
     for (so = head->so_next; so != head; so = so->so_next) {
-        if (so->so_fport == fport) {
+        addr_len = sizeof(addr);
+        if (getsockname(so->s, (struct sockaddr *)&addr, &addr_len) == 0 &&
+            addr.sin_port == port) {
             close(so->s);
             sofree(so);
             n++;