Author: eugen
Date: Wed Sep 12 08:46:49 2018
New Revision: 338611
URL: https://svnweb.freebsd.org/changeset/base/338611

Log:
  MFC r338468: Fix "ipfw fwd" to work for incoming IPv4 packets
  when ip_tryforward() chooses fast forwarding path, as it already works
  for IPv6 and for both of them on old slow path.
  
  PR:                   231143
  Reviewed by:          ae
  Differential Revision:        https://reviews.freebsd.org/D17039

Modified:
  stable/11/sys/netinet/ip_fastfwd.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/netinet/ip_fastfwd.c
==============================================================================
--- stable/11/sys/netinet/ip_fastfwd.c  Wed Sep 12 08:13:54 2018        
(r338610)
+++ stable/11/sys/netinet/ip_fastfwd.c  Wed Sep 12 08:46:49 2018        
(r338611)
@@ -151,7 +151,7 @@ ip_tryforward(struct mbuf *m)
        struct mbuf *m0 = NULL;
        struct nhop4_basic nh;
        struct sockaddr_in dst;
-       struct in_addr odest, dest;
+       struct in_addr dest, odest, rtdest;
        uint16_t ip_len, ip_off;
        int error = 0;
        struct m_tag *fwd_tag = NULL;
@@ -292,12 +292,31 @@ passin:
 #endif
 
        /*
+        * Next hop forced by pfil(9) hook?
+        */
+       if ((m->m_flags & M_IP_NEXTHOP) &&
+           ((fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL)) {
+               /*
+                * Now we will find route to forced destination.
+                */
+               dest.s_addr = ((struct sockaddr_in *)
+                           (fwd_tag + 1))->sin_addr.s_addr;
+               m_tag_delete(m, fwd_tag);
+               m->m_flags &= ~M_IP_NEXTHOP;
+       }
+
+       /*
         * Find route to destination.
         */
        if (ip_findroute(&nh, dest, m) != 0)
                return (NULL);  /* icmp unreach already sent */
 
        /*
+        * Avoid second route lookup by caching destination.
+        */
+       rtdest.s_addr = dest.s_addr;
+
+       /*
         * Step 5: outgoing firewall packet processing
         */
        if (!PFIL_HOOKED(&V_inet_pfil_hook))
@@ -319,6 +338,8 @@ passin:
         */
        if (m->m_flags & M_IP_NEXTHOP)
                fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
+       else
+               fwd_tag = NULL;
        if (odest.s_addr != dest.s_addr || fwd_tag != NULL) {
                /*
                 * Is it now for a local address on this host?
@@ -340,7 +361,8 @@ forwardlocal:
                        m_tag_delete(m, fwd_tag);
                        m->m_flags &= ~M_IP_NEXTHOP;
                }
-               if (ip_findroute(&nh, dest, m) != 0)
+               if (dest.s_addr != rtdest.s_addr &&
+                   ip_findroute(&nh, dest, m) != 0)
                        return (NULL);  /* icmp unreach already sent */
        }
 
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