From: Marcelo Ricardo Leitner <[email protected]> Date: Mon, 5 Dec 2016 18:37:13 -0200
> There have been some reports lately about TCP connection stalls caused > by NIC drivers that aren't setting gso_size on aggregated packets on rx > path. This causes TCP to assume that the MSS is actually the size of the > aggregated packet, which is invalid. > > Although the proper fix is to be done at each driver, it's often hard > and cumbersome for one to debug, come to such root cause and report/fix > it. > > This patch amends this situation in two ways. First, it adds a warning > on when this situation occurs, so it gives a hint to those trying to > debug this. It also limit the maximum probed MSS to the adverised MSS, > as it should never be any higher than that. > > The result is that the connection may not have the best performance ever > but it shouldn't stall, and the admin will have a hint on what to look > for. > > Tested with virtio by forcing gso_size to 0. > > v2: updated msg per David's suggestion > v3: use skb_iif to find the interface and also log its name, per Eric > Dumazet's suggestion. As the skb may be backlogged and the interface > gone by then, we need to check if the number still has a meaning. > v4: use helper tcp_gro_dev_warn() and avoid pr_warn_once inside __once, per > David's suggestion > > Cc: Jonathan Maxwell <[email protected]> > Signed-off-by: Marcelo Ricardo Leitner <[email protected]> Applied, thanks Marcelo.
