Date: Fri, 19 Jan 2018 16:52:09 -0500 From: Ryan Stone <rysto32@gmail.com> To: freebsd-net <freebsd-net@freebsd.org>, "<freebsd-transport@freebsd.org>" <freebsd-transport@freebsd.org> Subject: 3 ARP cache related reviews Message-ID: <CAFMmRNzXvwuHqyqJUte6FsPcR7hknSnc4Q8J67yumETnHyaCSQ@mail.gmail.com>
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I've opened 3 phabricator reviews fixing issues with the inpcb llentry caching. https://reviews.freebsd.org/D13988 This fix invalidates the llentry cache after the L3 route cache was invalidated by the routing table's generation count incrementing. Without this fix existing connections would continue to use stale L2 headers after the routing table was updated. I tried a simple test where I added a new route that would change the routing of an active TCP connection and confirmed with tcpdump that without this fix, the stack continues to use the old src/dst MAC for the original route. This caused the traffic to be blackholed at the new gateway as the MAC did not match. https://reviews.freebsd.org/D13989 This is a simple cleanup of the inpcb cache invalidation. Rather than copy-and-pasting the separate invalidation of the L2 cache and the L3 cache, I move the invalidation into a single macro and invoke it everywhere that needs to drop the cache. This will hopefully prevent future bugs like D13988 from occurring in new code. https://reviews.freebsd.org/D13990 This fixes an issue where the inpcb L2 cache was not updated following a change to a route's gateway. This led the connection to continue to use the old gateway. If the old gateway stopping routing traffic this would cause the connection to be blackholed. My fix here is more heavy-handed than it needs to be, as I just increment the route table generation count, which will cause all connections to drop their L2 and L3 caches. This could be made more selective by adding a generation count to each route entry, but I don't believe that route table modifications will happen frequently enough for anybody to care. Please speak up if you believe differently. If you're interested in one or more of these changes, please subscribe yourself to the reviews. I don't subscribe mailing lists to reviews to reduce the spam on the lists. Thanks, Ryan
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