slirp: Add a special case for the NULL socket

NULL sockets are used for NDP, BOOTP, and other critical operations.
If the topmost mbuf in a NULL session is blocked pending resolution,
it may cause problems if it blocks other packets with a NULL socket.
So do not add mbufs with a NULL socket field to the same session.

Signed-off-by: Kevin Cernekee <cernekee@chromium.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

1 files changed, 9 insertions, 7 deletions

diff --git a/if.c b/if.c
index 05a2784..e72a891 100644
--- a/if.c
+++ b/if.c
@@ -70,13 +70,15 @@ void if_output(struct socket *so, struct mbuf *ifm)
      * order)
      * XXX add cache here?
      */
-    for (ifq = (struct mbuf *)slirp->if_batchq.qh_rlink;
-         (struct quehead *)ifq != &slirp->if_batchq; ifq = ifq->ifq_prev) {
-        if (so == ifq->ifq_so) {
-            /* A match! */
-            ifm->ifq_so = so;
-            ifs_insque(ifm, ifq->ifs_prev);
-            goto diddit;
+    if (so) {
+        for (ifq = (struct mbuf *)slirp->if_batchq.qh_rlink;
+             (struct quehead *)ifq != &slirp->if_batchq; ifq = ifq->ifq_prev) {
+            if (so == ifq->ifq_so) {
+                /* A match! */
+                ifm->ifq_so = so;
+                ifs_insque(ifm, ifq->ifs_prev);
+                goto diddit;
+            }
         }
     }