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Message-ID: <20230804175700.1f88604b@kernel.org> Date: Fri, 4 Aug 2023 17:57:00 -0700 From: Jakub Kicinski <kuba@...nel.org> To: Hannes Reinecke <hare@...e.de> Cc: Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, Keith Busch <kbusch@...nel.org>, linux-nvme@...ts.infradead.org, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org Subject: Re: [PATCH] net/tls: avoid TCP window full during ->read_sock() On Thu, 3 Aug 2023 12:08:09 +0200 Hannes Reinecke wrote: > When flushing the backlog after decoding each record in ->read_sock() > we may end up with really long records, causing a TCP window full as > the TCP window would only be increased again after we process the > record. So we should rather process the record first to allow the > TCP window to be increased again before flushing the backlog. > - released = tls_read_flush_backlog(sk, prot, rxm->full_len, to_decrypt, > - decrypted, &flushed_at); > skb = darg.skb; > + /* TLS 1.3 may have updated the length by more than overhead */ > + rxm = strp_msg(skb); > + tlm = tls_msg(skb); > decrypted += rxm->full_len; > > tls_rx_rec_done(ctx); > @@ -2280,6 +2275,12 @@ int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc, > goto read_sock_requeue; > } > copied += used; > + /* > + * flush backlog after processing the TLS record, otherwise we might > + * end up with really large records and triggering a TCP window full. > + */ > + released = tls_read_flush_backlog(sk, prot, decrypted - copied, decrypted, > + copied, &flushed_at); I'm surprised moving the flushing out makes a difference. rx_list should generally hold at most 1 skb (16kB) unless something is PEEKing the data. Looking at it closer I think the problem may be calling args to tls_read_flush_backlog(). Since we don't know how much data reader wants we can't sensibly evaluate the first condition, so how would it work if instead of this patch we did: - released = tls_read_flush_backlog(sk, prot, rxm->full_len, to_decrypt, + released = tls_read_flush_backlog(sk, prot, INT_MAX, 0, decrypted, &flushed_at); That would give us a flush every 128k of data (or every record if inq is shorter than 16kB). side note - I still prefer 80 char max lines, please. It seems to result in prettier code ovarall as it forces people to think more about code structure. > if (used < rxm->full_len) { > rxm->offset += used; > rxm->full_len -= used; -- pw-bot: cr
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