On Fri, Dec 18, 2015 at 06:38:03PM -0800, Eric Dumazet wrote: > On Fri, 2015-12-18 at 19:58 +0100, Willy Tarreau wrote: > > Hi Josh, > > > > On Fri, Dec 18, 2015 at 08:33:45AM -0800, Josh Snyder wrote: > > > I was also puzzled that binding succeeded. Looking into the code paths > > > involved, in inet_csk_get_port, we quickly goto have_snum. From there, we > > > end > > > up dropping into tb_found. Since !hlist_empty(&tb->owners), we end up > > > checking > > > that (tb->fastreuseport > 0 && sk->sk_reuseport && uid_eq(tb->fastuid, > > > uid)). > > > This test passes, so we goto success and bind. > > > > > > Crucially, we are checking the fastreuseport field on the > > > inet_bind_bucket, and > > > not the sk_reuseport variable on the other sockets in the bucket. Since > > > this > > > bit is set based on sk_reuseport at the time the first socket binds (see > > > tb_not_found), I can see no reason why sockets need to keep SO_REUSEPORT > > > set > > > beyond initial binding. > > > > > > Given this, I believe Willy's patch elegantly solves the problem at hand. > > > > Great, thanks for your in-depth explanation. > > > > Eric, do you think that this patch may be acceptable material for next > > merge window (given that it's not a fix per-se) ? If so I'll resubmit > > later. > > I need to check with Craig Gallek, because he was about to upstream a > change to make SO_REUSEPORT more scalable & sexy (like having an [e]BPF > filter to perform the selection in an array of sockets)
OK fine. Please note that I also considered using a new value instead of zero there but I preferred to avoid it since the man talked about zero/ non-zero so I wanted to limit any API change. If Craig adds new values there then this is something we can reconsider. Have a nice week-end, Willy -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
