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Merge branch 'tcp-address-issues-with-ect0-not-being-set-in-dctcp-packets' 

Alexander Duyck says:

====================
tcp: Address issues with ECT0 not being set in DCTCP packets

This patch set is meant to address issues seen with SYN/ACK packets not
containing the ECT0 bit when DCTCP is configured as the congestion control
algorithm for a TCP socket.

A simple test using "tcpdump" and "test_progs -t bpf_tcp_ca" makes the
issue obvious. Looking at the packets will result in the SYN/ACK packet
with an ECT0 bit that does not match the other packets for the flow when
the congestion control agorithm is switch from the default. So for example
going from non-DCTCP to a DCTCP congestion control algorithm we will see
the SYN/ACK IPV6 header will not have ECT0 set while the other packets in
the flow will. Likewise if we switch from a default of DCTCP to cubic we
will see the ECT0 bit set in the SYN/ACK while the other packets in the
flow will not.
====================

Link: https://lore.kernel.org/r/160582070138.66684.11785214534154816097.stgit@localhost.localdomain
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2020-11-20 18:10:47 -08:00
parent d2624e70a2 55472017a4
commit e10823c719
3 changed files with 11 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
net/ipv4/tcp_cong.c
View File

@ -198,6 +198,11 @@ static void tcp_reinit_congestion_control(struct sock *sk,
icsk->icsk_ca_setsockopt = 1;
memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
if (ca->flags & TCP_CONG_NEEDS_ECN)
INET_ECN_xmit(sk);
else
INET_ECN_dontxmit(sk);
if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
tcp_init_congestion_control(sk);
}

5
net/ipv4/tcp_ipv4.c
View File

@ -981,7 +981,8 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
skb = tcp_make_synack(sk, dst, req, foc, synack_type, syn_skb);
tos = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ?
tcp_rsk(req)->syn_tos : inet_sk(sk)->tos;
tcp_rsk(req)->syn_tos & ~INET_ECN_MASK :
inet_sk(sk)->tos;
if (skb) {
__tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
@ -990,7 +991,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
ireq->ir_rmt_addr,
rcu_dereference(ireq->ireq_opt),
tos & ~INET_ECN_MASK);
tos);
rcu_read_unlock();
err = net_xmit_eval(err);
}

6
net/ipv6/tcp_ipv6.c
View File

@ -530,12 +530,12 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
rcu_read_lock();
opt = ireq->ipv6_opt;
tclass = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ?
tcp_rsk(req)->syn_tos : np->tclass;
tcp_rsk(req)->syn_tos & ~INET_ECN_MASK :
np->tclass;
if (!opt)
opt = rcu_dereference(np->opt);
err = ip6_xmit(sk, skb, fl6, sk->sk_mark, opt,
tclass & ~INET_ECN_MASK,
sk->sk_priority);
tclass, sk->sk_priority);
rcu_read_unlock();
err = net_xmit_eval(err);
}