Hello, Here is another approach: https://lkml.org/lkml/2018/12/5/1206 Matt On Wed, Apr 25, 2018 at 1:35 AM Mat Martineau <mathew.j.martineau(a)linux.intel.com&gt; wrote: > > > I noticed this patch on netdev to avoid an indirect call to md5_lookup, > which was accepted. It is mitigating the cost of an existing indirect call > rather than adding a new one, but shows how the maintainers are looking at > the problem. > > -- > Mat Martineau > Intel OTC > > ---------- Forwarded message ---------- > Date: Mon, 23 Apr 2018 14:46:25 > From: Eric Dumazet <edumazet(a)google.com&gt; > To: David S . Miller <davem(a)davemloft.net&gt; > Cc: netdev <netdev(a)vger.kernel.org&gt;, Eric Dumazet <edumazet(a)google.com&gt;, > Eric Dumazet <eric.dumazet(a)gmail.com&gt; > Subject: [PATCH net-next] tcp: md5: only call tp->af_specific->md5_lookup() for > md5 sockets > > RETPOLINE made calls to tp->af_specific->md5_lookup() quite expensive, > given they have no result. > We can omit the calls for sockets that have no md5 keys. > > Signed-off-by: Eric Dumazet <edumazet(a)google.com&gt; > --- > net/ipv4/tcp_output.c | 26 ++++++++++++++------------ > 1 file changed, 14 insertions(+), 12 deletions(-) > > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 383cac0ff0ec059ca7dbc1a6304cc7f8183e008d..95feffb6d53f8a9eadfb15a2fffeec498d6e993a 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -585,14 +585,15 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, > unsigned int remaining = MAX_TCP_OPTION_SPACE; > struct tcp_fastopen_request *fastopen = tp->fastopen_req; > > + *md5 = NULL; > #ifdef CONFIG_TCP_MD5SIG > - *md5 = tp->af_specific->md5_lookup(sk, sk); > - if (*md5) { > - opts->options |= OPTION_MD5; > - remaining -= TCPOLEN_MD5SIG_ALIGNED; > + if (unlikely(rcu_access_pointer(tp->md5sig_info))) { > + *md5 = tp->af_specific->md5_lookup(sk, sk); > + if (*md5) { > + opts->options |= OPTION_MD5; > + remaining -= TCPOLEN_MD5SIG_ALIGNED; > + } > } > -#else > - *md5 = NULL; > #endif > > /* We always get an MSS option. The option bytes which will be seen in > @@ -720,14 +721,15 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb > > opts->options = 0; > > + *md5 = NULL; > #ifdef CONFIG_TCP_MD5SIG > - *md5 = tp->af_specific->md5_lookup(sk, sk); > - if (unlikely(*md5)) { > - opts->options |= OPTION_MD5; > - size += TCPOLEN_MD5SIG_ALIGNED; > + if (unlikely(rcu_access_pointer(tp->md5sig_info))) { > + *md5 = tp->af_specific->md5_lookup(sk, sk); > + if (*md5) { > + opts->options |= OPTION_MD5; > + size += TCPOLEN_MD5SIG_ALIGNED; > + } > } > -#else > - *md5 = NULL; > #endif > > if (likely(tp->rx_opt.tstamp_ok)) { > -- > 2.17.0.484.g0c8726318c-goog > > _______________________________________________ > mptcp mailing list > mptcp(a)lists.01.org > https://lists.01.org/mailman/listinfo/mptcp -- Matthieu Baerts | R&D Engineer matthieu.baerts(a)tessares.net Tessares SA | Hybrid Access Solutions www.tessares.net 1 Avenue Jean Monnet, 1348 Louvain-la-Neuve, Belgium Disclaimer: https://www.tessares.net/mail-disclaimer/