From: Cong Wang <xiyou.wangc...@gmail.com> Date: Mon, 4 Apr 2016 13:45:02 -0700
> On Sat, Apr 2, 2016 at 7:33 PM, Martin KaFai Lau <ka...@fb.com> wrote: >> One thing to note is that this patch uses the addresses from the sk >> instead of iph when updating sk->sk_dst_cache. It is basically the >> same logic that the __ip6_datagram_connect() is doing, so some >> refactoring works in the first two patches. >> >> AFAIK, a UDP socket can become connected after sending out some >> datagrams in un-connected state. or It can be connected >> multiple times to different destinations. I did some quick >> tests but I could be wrong. >> >> I am thinking if there could be a chance that the skb->data, which >> has the original outgoing iph, is not related to the current >> connected address. If it is possible, we have to specifically >> use the addresses in the sk instead of skb->data (i.e. iph) when >> updating the sk->sk_dst_cache. >> >> If we need to use the sk addresses (and other info) to find out a >> new dst for a connected udp socket, it is better not doing it while >> the userland is connecting to somewhere else. >> >> If the above case is impossible, we can keep using the info from iph to >> do the dst update for a connected-udp sk without taking the lock. > > I see your point, but calling __ip6_datagram_connect() seems overkill > here, we don't need to update so many things in the pmtu update context, > at least IPv4 doesn't do that either. I don't think you have to do that. > > So why just updating the dst cache (also some addr cache) here is not > enough? I think we are steadily getting closer to a version of this fix that we have some agreement on, right? Martin can you address Cong's feedback and spin another version of this series? Thanks.
