svn commit: r196770 - in stable/8/sys: . amd64/include/xen cddl/contrib/opensolaris contrib/dev/acpica contrib/pf dev/xen/xenpci netinet

[Bjoern A. Zeeb]

Author: bz
Date: Wed Sep  2 16:35:57 2009
New Revision: 196770
URL: http://svn.freebsd.org/changeset/base/196770

Log:
  MFC r196738:
    In case an upper layer protocol tries to send a packet but the
    L2 code does not have the ethernet address for the destination
    within the broadcast domain in the table, we remember the
    original mbuf in `la_hold' in arpresolve() and send out a
    different packet with an arp request.
    In case there will be more upper layer packets to send we will
    free an earlier one held in `la_hold' and queue the new one.
  
    Once we get a packet in, with which we can perfect our arp table
    entry we send out the original 'on hold' packet, should there
    be any.
    Rather than continuing to process the packet that we received,
    we returned without freeing the packet that came in, which
    basically means that we leaked an mbuf for every arp request
    we sent.
  
    Rather than freeing the received packet and returning, continue
    to process the incoming arp packet as well.
    This should (a) improve some setups, also proxy-arp, in case it was an
    incoming arp request and (b) resembles the behaviour FreeBSD had
    from day 1, which alignes with RFC826 "Packet reception" (merge case).
  
    Rename 'm0' to 'hold' to make the code more understandable as
    well as diffable to earlier versions more easily.
  
    Handle the link-layer entry 'la' lock comepletely in the block
    where needed and release it as early as possible, rather than
    holding it longer, down to the end of the function.
  
    Found by:			pointyhat, ns1
    Bug hunting session with:	erwin, simon, rwatson
    Tested by:			simon on cluster machines
    Reviewed by:			ratson, kmacy, julian
  
  Approved by:	re (kib)

Modified:
  stable/8/sys/   (props changed)
  stable/8/sys/amd64/include/xen/   (props changed)
  stable/8/sys/cddl/contrib/opensolaris/   (props changed)
  stable/8/sys/contrib/dev/acpica/   (props changed)
  stable/8/sys/contrib/pf/   (props changed)
  stable/8/sys/dev/xen/xenpci/   (props changed)
  stable/8/sys/netinet/if_ether.c

Modified: stable/8/sys/netinet/if_ether.c
==============================================================================
--- stable/8/sys/netinet/if_ether.c	Wed Sep  2 16:02:48 2009	(r196769)
+++ stable/8/sys/netinet/if_ether.c	Wed Sep  2 16:35:57 2009	(r196770)
@@ -462,11 +462,11 @@ in_arpinput(struct mbuf *m)
 	struct rtentry *rt;
 	struct ifaddr *ifa;
 	struct in_ifaddr *ia;
+	struct mbuf *hold;
 	struct sockaddr sa;
 	struct in_addr isaddr, itaddr, myaddr;
 	u_int8_t *enaddr = NULL;
 	int op, flags;
-	struct mbuf *m0;
 	int req_len;
 	int bridged = 0, is_bridge = 0;
 #ifdef DEV_CARP
@@ -631,11 +631,13 @@ match:
 				    la->lle_tbl->llt_ifp->if_xname,
 				    ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
 				    ifp->if_xname);
+			LLE_WUNLOCK(la);
 			goto reply;
 		}
 		if ((la->la_flags & LLE_VALID) &&
 		    bcmp(ar_sha(ah), &la->ll_addr, ifp->if_addrlen)) {
 			if (la->la_flags & LLE_STATIC) {
+				LLE_WUNLOCK(la);
 				log(LOG_ERR,
 				    "arp: %*D attempts to modify permanent "
 				    "entry for %s on %s\n",
@@ -655,6 +657,7 @@ match:
 		}
 		    
 		if (ifp->if_addrlen != ah->ar_hln) {
+			LLE_WUNLOCK(la);
 			log(LOG_WARNING,
 			    "arp from %*D: addr len: new %d, i/f %d (ignored)",
 			    ifp->if_addrlen, (u_char *) ar_sha(ah), ":",
@@ -671,15 +674,14 @@ match:
 		}
 		la->la_asked = 0;
 		la->la_preempt = V_arp_maxtries;
-		if (la->la_hold != NULL) {
-			m0 = la->la_hold;
-			la->la_hold = 0;
+		hold = la->la_hold;
+		if (hold != NULL) {
+			la->la_hold = NULL;
 			memcpy(&sa, L3_ADDR(la), sizeof(sa));
-			LLE_WUNLOCK(la);
-			
-			(*ifp->if_output)(ifp, m0, &sa, NULL);
-			return;
 		}
+		LLE_WUNLOCK(la);
+		if (hold != NULL)
+			(*ifp->if_output)(ifp, hold, &sa, NULL);
 	}
 reply:
 	if (op != ARPOP_REQUEST)
@@ -750,8 +752,6 @@ reply:
 #endif
 	}
 
-	if (la != NULL)
-		LLE_WUNLOCK(la);
 	if (itaddr.s_addr == myaddr.s_addr &&
 	    IN_LINKLOCAL(ntohl(itaddr.s_addr))) {
 		/* RFC 3927 link-local IPv4; always reply by broadcast. */
@@ -777,8 +777,6 @@ reply:
 	return;
 
 drop:
-	if (la != NULL)
-		LLE_WUNLOCK(la);
 	m_freem(m);
 }
 #endif