kern/168190: [pf] panic when using pf and route-to (maybe: bad fragment handling?)

[Daniel Hartmeier]

Here's a patch that directly tests this theory.

If correct, it will replace the panics with simple log messages that
show when ipfilter left an m_len==0 mbuf.

Daniel

Index: sys/contrib/ipfilter/netinet/ip_fil_freebsd.c
===================================================================
RCS file: /home/ncvs/src/sys/contrib/ipfilter/netinet/ip_fil_freebsd.c,v
retrieving revision 1.20.4.1
diff -u -r1.20.4.1 ip_fil_freebsd.c
--- sys/contrib/ipfilter/netinet/ip_fil_freebsd.c       23 Sep 2011 00:51:37 -0000      1.20.4.1
+++ sys/contrib/ipfilter/netinet/ip_fil_freebsd.c       4 Jun 2012 10:19:04 -0000
@@ -182,8 +182,18 @@
 static int
 fr_check_wrapper(void *arg, struct mbuf **mp, struct ifnet *ifp, int dir)
 {
+       int r;
+
        struct ip *ip = mtod(*mp, struct ip *);
-       return fr_check(ip, ip->ip_hl << 2, ifp, (dir == PFIL_OUT), mp);
+       ASSERT_HOST_BYTE_ORDER(*mp);
+       r = fr_check(ip, ip->ip_hl << 2, ifp, (dir == PFIL_OUT), mp);
+       if (*mp != NULL && (*mp)->m_pkthdr.len >= sizeof(struct ip) &&
+           (*mp)->m_len < sizeof(struct ip)) {
+               printf("fr_check_wrapper: m_len %d fixed\n",
+                   (int)(*mp)->m_len);
+               *mp = m_pullup(*mp, sizeof(struct ip));
+       }
+       return r;
 }

 # ifdef USE_INET6