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From: Xin LI <delphij@FreeBSD.org>
Date: Tue, 7 Apr 2015 20:20:10 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r281229 - head/sys/netinet6
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Author: delphij
Date: Tue Apr  7 20:20:09 2015
New Revision: 281229
URL: https://svnweb.freebsd.org/changeset/base/281229

Log:
  Mitigate Local Denial of Service with IPv6 Router Advertisements
  and log attack attempts.
  
  Submitted by:	hrs
  Security:	FreeBSD-SA-15:09.nd6
  Security:	CVE-2015-2923

Modified:
  head/sys/netinet6/nd6_rtr.c

Modified: head/sys/netinet6/nd6_rtr.c
==============================================================================
--- head/sys/netinet6/nd6_rtr.c	Tue Apr  7 20:20:03 2015	(r281228)
+++ head/sys/netinet6/nd6_rtr.c	Tue Apr  7 20:20:09 2015	(r281229)
@@ -297,8 +297,16 @@ nd6_ra_input(struct mbuf *m, int off, in
 	}
 	if (nd_ra->nd_ra_retransmit)
 		ndi->retrans = ntohl(nd_ra->nd_ra_retransmit);
-	if (nd_ra->nd_ra_curhoplimit)
-		ndi->chlim = nd_ra->nd_ra_curhoplimit;
+	if (nd_ra->nd_ra_curhoplimit) {
+		if (ndi->chlim < nd_ra->nd_ra_curhoplimit)
+			ndi->chlim = nd_ra->nd_ra_curhoplimit;
+		else if (ndi->chlim != nd_ra->nd_ra_curhoplimit) {
+			log(LOG_ERR, "RA with a lower CurHopLimit sent from "
+			    "%s on %s (current = %d, received = %d). "
+			    "Ignored.\n", ip6_sprintf(ip6bufs, &ip6->ip6_src),
+			    if_name(ifp), ndi->chlim, nd_ra->nd_ra_curhoplimit);
+		}
+	}
 	dr = defrtrlist_update(&dr0);
     }