On Mon, Jul 17, 2017 at 01:51:51AM -0700, Eric Dumazet wrote: > On Thu, 2017-07-13 at 10:56 -0700, Shaohua Li wrote: > > From: Shaohua Li <s...@fb.com> > > > > Please see below tcpdump output: > > > The tcp reset packet has a different flowlabel, which causes our router > > doesn't correctly close tcp connection. > > This looks a bug in your router, because (IPv6 only) flowlabel is not > part of the tuple identifying a TCP flow.
Actually it's for load balance between several routers. > > > The reason is the normal packet > > gets the skb->hash from sk->sk_txhash, which is generated randomly. > > ip6_make_flowlabel then uses the hash to create a flowlabel. The reset > > packet doesn't get assigned a hash, so the flowlabel is calculated with > > flowi6. > > > > The solution is to save the hash value for timeout sock and use it for > > reset packet. > > I am a bit unsure why we need to add yet another field in TCP timewait > structure, since : > > 1) flowlabel can vary during a TCP flow lifetime. > 2) flowlabel is different unde synflood (each syncookie gets a random > flowlabel), and if 3rd packet comes back from the client to finish 3WHS, > the flowlabel will again be different from the one that SYNACK used. Is it acceptable we reuse tw_flowlabel as Florent Fourcot suggested? It makes no sense to change flowlabel for no reason. Thanks, Shaohua
