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From: Robert Watson <rwatson@FreeBSD.org>
Date: Thu, 21 May 2009 09:45:47 +0000 (UTC)
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Subject: svn commit: r192528 - head/sys/netinet
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Author: rwatson
Date: Thu May 21 09:45:47 2009
New Revision: 192528
URL: http://svn.freebsd.org/changeset/base/192528

Log:
  Consolidate and clean up the first section of ip_output.c in light of the
  last year or two's work on routing:
  
  - Combine iproute initialization and flowtable lookup blocks, eliminating
    unnecessary tests for known-zero'd iproute fields.
  
  - Add a comment indicating (a) why the route entry returned by the
    flowtable is considered stable and (b) that the flowtable lookup must
    occur after the setup of the mbuf flow ID.
  
  - Assert the inpcb lock before any use of inpcb fields.
  
  Reviewed by:	kmacy

Modified:
  head/sys/netinet/ip_output.c

Modified: head/sys/netinet/ip_output.c
==============================================================================
--- head/sys/netinet/ip_output.c	Thu May 21 07:55:25 2009	(r192527)
+++ head/sys/netinet/ip_output.c	Thu May 21 09:45:47 2009	(r192528)
@@ -150,20 +150,25 @@ ip_output(struct mbuf *m, struct mbuf *o
 #endif
 	M_ASSERTPKTHDR(m);
 
-	if (ro == NULL) {
-		ro = &iproute;
-		bzero(ro, sizeof (*ro));
-	}
-
 	if (inp != NULL) {
-		M_SETFIB(m, inp->inp_inc.inc_fibnum);
 		INP_LOCK_ASSERT(inp);
+		M_SETFIB(m, inp->inp_inc.inc_fibnum);
 		if (inp->inp_flags & (INP_HW_FLOWID|INP_SW_FLOWID)) {
 			m->m_pkthdr.flowid = inp->inp_flowid;
 			m->m_flags |= M_FLOWID;
 		}
 	}
-	if ((ro == &iproute) && (ro->ro_rt == NULL) && (ro->ro_lle == NULL)) {
+
+	if (ro == NULL) {
+		ro = &iproute;
+		bzero(ro, sizeof (*ro));
+
+		/*
+		 * The flow table returns route entries valid for up to 30
+		 * seconds; we rely on the remainder of ip_output() taking no
+		 * longer than that long for the stability of ro_rt.  The
+		 * flow ID assignment must have happened before this point.
+		 */
 		if (flowtable_lookup(ip_ft, m, ro) == 0)
 			nortfree = 1;
 	}