Attached is an MFC candidate for a patch I just merged to 8.x, which corrects the UDP lock recursion issue both of you were running into. If it settles well for a couple of days in HEAD then I'll go ahead and request an MFC from re@, but your confirmation as to whether or not this corrects the specific symptoms you are seeing would be very helpful. I was able to confirm that it eliminated what appeared to be the same problem here when I attempted to reproduce it based on the information you provided, so I'm hopeful.\

Thanks,

Robert N M Watson
Computer Laboratory
University of Cambridge


Property changes on: .
___________________________________________________________________
Modified: svn:mergeinfo
   Merged /head/sys:r183265

Index: netinet6/udp6_usrreq.c
===================================================================
--- netinet6/udp6_usrreq.c      (revision 183265)
+++ netinet6/udp6_usrreq.c      (working copy)
@@ -975,13 +975,23 @@
                                error = EINVAL;
                                goto out;
                        }
+
+                       /*
+                        * XXXRW: We release UDP-layer locks before calling
+                        * udp_send() in order to avoid recursion.  However,
+                        * this does mean there is a short window where inp's
+                        * fields are unstable.  Could this lead to a
+                        * potential race in which the factors causing us to
+                        * select the UDPv4 output routine are invalidated?
+                        */
+                       INP_WUNLOCK(inp);
+                       INP_INFO_WUNLOCK(&udbinfo);
                        if (sin6)
                                in6_sin6_2_sin_in_sock(addr);
                        pru = inetsw[ip_protox[IPPROTO_UDP]].pr_usrreqs;
-                       error = ((*pru->pru_send)(so, flags, m, addr, control,
+                       /* addr will just be freed in sendit(). */
+                       return ((*pru->pru_send)(so, flags, m, addr, control,
                            td));
-                       /* addr will just be freed in sendit(). */
-                       goto out;
                }
        }
 #endif
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