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Date:      Tue, 16 Dec 2008 23:06:36 +0000 (UTC)
From:      Kip Macy <kmacy@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r186196 - head/sys/netinet6
Message-ID:  <200812162306.mBGN6agp049992@svn.freebsd.org>
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Author: kmacy
Date: Tue Dec 16 23:06:36 2008
New Revision: 186196
URL: http://svn.freebsd.org/changeset/base/186196

Log:
  - Simplify handling of the deferring of mbuf transmit until after lle lock drop
  - add a couple of comments to clarify intent

Modified:
  head/sys/netinet6/nd6.c

Modified: head/sys/netinet6/nd6.c
==============================================================================
--- head/sys/netinet6/nd6.c	Tue Dec 16 22:16:34 2008	(r186195)
+++ head/sys/netinet6/nd6.c	Tue Dec 16 23:06:36 2008	(r186196)
@@ -1407,7 +1407,7 @@ nd6_cache_lladdr(struct ifnet *ifp, stru
 	int newstate = 0;
 	uint16_t router = 0;
 	struct sockaddr_in6 sin6;
-	struct mbuf *tail = NULL, *chain = NULL;
+	struct mbuf *chain = NULL;
 	int static_route = 0;
 
 	IF_AFDATA_UNLOCK_ASSERT(ifp);
@@ -1526,11 +1526,14 @@ nd6_cache_lladdr(struct ifnet *ifp, stru
 					 * just set the 2nd argument as the
 					 * 1st one.
 					 */
-					nd6_output_lle(ifp, ifp, m_hold, L3_ADDR_SIN6(ln), NULL, ln, &tail);
-					if ((tail != NULL) && chain == (NULL))
-						chain = tail;					
+					nd6_output_lle(ifp, ifp, m_hold, L3_ADDR_SIN6(ln), NULL, ln, &chain);
 				}
-				if (chain)
+				/*
+				 * If we have mbufs in the chain we need to do
+				 * deferred transmit. Copy the address from the
+				 * llentry before dropping the lock down below.
+				 */
+				if (chain != NULL)
 					memcpy(&sin6, L3_ADDR_SIN6(ln), sizeof(sin6));
 			}
 		} else if (ln->ln_state == ND6_LLINFO_INCOMPLETE) {
@@ -1706,7 +1709,7 @@ nd6_output(struct ifnet *ifp, struct ifn
 int
 nd6_output_lle(struct ifnet *ifp, struct ifnet *origifp, struct mbuf *m0,
     struct sockaddr_in6 *dst, struct rtentry *rt0, struct llentry *lle,
-	struct mbuf **tail)
+	struct mbuf **chain)
 {
 	INIT_VNET_INET6(curvnet);
 	struct mbuf *m = m0;
@@ -1720,7 +1723,7 @@ nd6_output_lle(struct ifnet *ifp, struct
 		
 		LLE_WLOCK_ASSERT(lle);
 
-		KASSERT(tail != NULL, (" lle locked but no tail pointer passed"));
+		KASSERT(chain != NULL, (" lle locked but no mbuf chain pointer passed"));
 	}
 #endif
 	if (IN6_IS_ADDR_MULTICAST(&dst->sin6_addr))
@@ -1888,12 +1891,25 @@ nd6_output_lle(struct ifnet *ifp, struct
 #ifdef MAC
 	mac_netinet6_nd6_send(ifp, m);
 #endif
+	/*
+	 * We were passed in a pointer to an lle with the lock held 
+	 * this means that we can't call if_output as we will
+	 * recurse on the lle lock - so what we do is we create
+	 * a list of mbufs to send and transmit them in the caller
+	 * after the lock is dropped
+	 */
 	if (lle != NULL) {
-		if (*tail == NULL)
-			*tail = m;
-		else {			
-			(*tail)->m_nextpkt = m;
-			*tail = m;			
+		if (*chain == NULL)
+			*chain = m;
+		else {
+			struct mbuf *m = *chain;
+
+			/*
+			 * append mbuf to end of deferred chain
+			 */
+			while (m->m_nextpkt != NULL)
+				m = m->m_nextpkt;
+			m->m_nextpkt = m;
 		}
 		return (error);
 	}

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