From a435903dcfb8ebb2897a36f22e743656e6314f02 Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Thu, 10 Sep 2020 15:35:32 -0400 Subject: [PATCH] tcp: Only init congestion control if not initialized already Change tcp_init_transfer() to only initialize congestion control if it has not been initialized already. With this new approach, we can arrange things so that if the EBPF code sets the congestion control by calling setsockopt(TCP_CONGESTION) then tcp_init_transfer() will not re-initialize the CC module. This is an approach that has the following beneficial properties: (1) This allows CC module customizations made by the EBPF called in tcp_init_transfer() to persist, and not be wiped out by a later call to tcp_init_congestion_control() in tcp_init_transfer(). (2) Does not flip the order of EBPF and CC init, to avoid causing bugs for existing code upstream that depends on the current order. (3) Does not cause 2 initializations for for CC in the case where the EBPF called in tcp_init_transfer() wants to set the CC to a new CC algorithm. (4) Allows follow-on simplifications to the code in net/core/filter.c and net/ipv4/tcp_cong.c, which currently both have some complexity to special-case CC initialization to avoid double CC initialization if EBPF sets the CC. Signed-off-by: Neal Cardwell Signed-off-by: Eric Dumazet Signed-off-by: Alexei Starovoitov Acked-by: Yuchung Cheng Acked-by: Kevin Yang Cc: Lawrence Brakmo --- include/net/inet_connection_sock.h | 3 ++- net/ipv4/tcp.c | 1 + net/ipv4/tcp_cong.c | 3 ++- net/ipv4/tcp_input.c | 4 +++- 4 files changed, 8 insertions(+), 3 deletions(-) diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index c738abeb3265c..dc763ca9413cc 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -96,7 +96,8 @@ struct inet_connection_sock { void (*icsk_clean_acked)(struct sock *sk, u32 acked_seq); struct hlist_node icsk_listen_portaddr_node; unsigned int (*icsk_sync_mss)(struct sock *sk, u32 pmtu); - __u8 icsk_ca_state:6, + __u8 icsk_ca_state:5, + icsk_ca_initialized:1, icsk_ca_setsockopt:1, icsk_ca_dst_locked:1; __u8 icsk_retransmits; diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 57a5688755391..7360d3db2b616 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2698,6 +2698,7 @@ int tcp_disconnect(struct sock *sk, int flags) if (icsk->icsk_ca_ops->release) icsk->icsk_ca_ops->release(sk); memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); + icsk->icsk_ca_initialized = 0; tcp_set_ca_state(sk, TCP_CA_Open); tp->is_sack_reneg = 0; tcp_clear_retrans(tp); diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 62878cf26d9cc..d18d7a1ce4ce7 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -176,7 +176,7 @@ void tcp_assign_congestion_control(struct sock *sk) void tcp_init_congestion_control(struct sock *sk) { - const struct inet_connection_sock *icsk = inet_csk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); tcp_sk(sk)->prior_ssthresh = 0; if (icsk->icsk_ca_ops->init) @@ -185,6 +185,7 @@ void tcp_init_congestion_control(struct sock *sk) INET_ECN_xmit(sk); else INET_ECN_dontxmit(sk); + icsk->icsk_ca_initialized = 1; } static void tcp_reinit_congestion_control(struct sock *sk, diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 4337841faeff9..0e5ac0d33fd3f 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5894,8 +5894,10 @@ void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb) tp->snd_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk)); tp->snd_cwnd_stamp = tcp_jiffies32; + icsk->icsk_ca_initialized = 0; bpf_skops_established(sk, bpf_op, skb); - tcp_init_congestion_control(sk); + if (!icsk->icsk_ca_initialized) + tcp_init_congestion_control(sk); tcp_init_buffer_space(sk); } -- 2.39.5