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Message-ID: <2134F8430051B64F815C691A62D9831816F612@XCH-BLV-504.nw.nos.boeing.com> Date: Thu, 5 Dec 2013 19:39:52 +0000 From: "Templin, Fred L" <Fred.L.Templin@...ing.com> To: "netdev@...r.kernel.org" <netdev@...r.kernel.org> Subject: Possible IPv6 fragmentation/pmtud bug Hi, I have the following test network configuration (all linux nodes running the 3.10.17 kernel): h1 <-----------> r1 <-----------> r2 <-----------> h2 8000 MTU link 4000 MTU link 8000 MTU link When host h1 ping6's host h2, routers r1 and r2 forward the ICMPv6 echo request/reply packets as expected. But, when I set a ping6 packet size that is larger than the router-to-router link MTU: h1# ping6 -s 5000 h2 router r1 does NOT send an ICMPv6 Packet Too Big message back to host h1 but rather fragments the ICMPv6 echo request packets itself before forwarding on to router r2 then ultimately host h1. The ping6's still succeed because of IPv6 fragmentation, but it is *router r1* that is doing the fragmentation instead of host h1. This seems to be related to the setting of the "skb->local_df" flag, which should only be set for locally-generated packets; not for packets that are being forwarded by a router. Does anyone have any idea as to why my router is performing fragmentation when it forwards an ICMPv6 packet? Thanks - Fred fred.l.templin@...ing.com -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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