> We had been using the auto_flowlabels=1 (i.e. essentially enable flowlabel) > mainly because we want to take the benefit of dst_negative_advice() when > tcp_write_timeout() happens. > > During our test, our system handles quite well with changing flowlabel. > The only exception we have hit is the TCP_RST sent from an inet_timewait_sock. > Martin,
That is interesting data. Have you determined why the middlebox has a problem with flow label change in TW state but not other states? Tom > If we keep the flowlabel consistent (or persistent sk_txhash), there > is no practical usage for us to turn on flowlabel and the problem also goes > away. We have it off for now. > >> >> > There seems to have other bug in this side. From my understanding, commit >> > 265f94ff54d6(net: Recompute sk_txhash on negative routing advice) tries to >> > select a different route. But the multipath selection code >> > (rt6_multipath_select) doesn't use sk_txhash or skb->hash, it does use >> > fl6.flowlabel, but that is the flowlabel user sets. So looks like the >> > commit >> > doesn't change anything. >> > >> The routing functions typically don't use sock of skbuff, but use flow >> structs instead. It may be reasonable to add a hash to those. > The localhost's mutlipath selection is another existing issue. AFAICT, > it does not take the sk_txhash (or skb->hash) into account and the following > dst_negative_advice() will also have no effect in the route selction. > It is another issue to be fixed and to be figured out how to pass the > sk_txhash down. (1) > > Shaohua is proposing to record the 20 bits of the sk_txhash in the > tw_flowlabel of the 'struct inet_timewait_sock'. The tw_flowlabel could > potentially be used to do the multipath selection once we figured out > how to tackle (1). > > Thanks, > Martin > > >> >> > What's the 'src port for UDP encap'? I can't find the code setting >> > skb->hash >> > to sk_txhash in UDP side. >> > >> udp_flow_src_port is function call by UDP encaps to set source port. >> This is call skb_get_hash. sk_set_txhash is function to set txhash >> right now to random value. skb_set_hash_from_sk set skb->hash when >> skbuff is owned by socket (skb_set_owner_w). >> >> Thanks, >> Tom >> >> >> > Thanks, >> > Shaohua
