From 55d8694fa82c9b5858ae5a78a210353961f908f9 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 26 Sep 2014 22:37:32 +0200 Subject: net: tcp: assign tcp cong_ops when tcp sk is created Split assignment and initialization from one into two functions. This is required by followup patches that add Datacenter TCP (DCTCP) congestion control algorithm - we need to be able to determine if the connection is moderated by DCTCP before the 3WHS has finished. As we walk the available congestion control list during the assignment, we are always guaranteed to have Reno present as it's fixed compiled-in. Therefore, since we're doing the early assignment, we don't have a real use for the Reno alias tcp_init_congestion_ops anymore and can thus remove it. Actual usage of the congestion control operations are being made after the 3WHS has finished, in some cases however we can access get_info() via diag if implemented, therefore we need to zero out the private area for those modules. Joint work with Daniel Borkmann and Glenn Judd. Signed-off-by: Florian Westphal Signed-off-by: Daniel Borkmann Signed-off-by: Glenn Judd Acked-by: Stephen Hemminger Signed-off-by: David S. Miller --- net/ipv4/tcp_cong.c | 46 ++++++++++++++++++++++------------------------ 1 file changed, 22 insertions(+), 24 deletions(-) (limited to 'net/ipv4/tcp_cong.c') diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 80248f56c89f..a6c8a5775624 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -74,24 +74,34 @@ void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); /* Assign choice of congestion control. */ -void tcp_init_congestion_control(struct sock *sk) +void tcp_assign_congestion_control(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_congestion_ops *ca; - /* if no choice made yet assign the current value set as default */ - if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) { - rcu_read_lock(); - list_for_each_entry_rcu(ca, &tcp_cong_list, list) { - if (try_module_get(ca->owner)) { - icsk->icsk_ca_ops = ca; - break; - } - - /* fallback to next available */ + rcu_read_lock(); + list_for_each_entry_rcu(ca, &tcp_cong_list, list) { + if (likely(try_module_get(ca->owner))) { + icsk->icsk_ca_ops = ca; + goto out; } - rcu_read_unlock(); + /* Fallback to next available. The last really + * guaranteed fallback is Reno from this list. + */ } +out: + rcu_read_unlock(); + + /* Clear out private data before diag gets it and + * the ca has not been initialized. + */ + if (ca->get_info) + memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); +} + +void tcp_init_congestion_control(struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); if (icsk->icsk_ca_ops->init) icsk->icsk_ca_ops->init(sk); @@ -345,15 +355,3 @@ struct tcp_congestion_ops tcp_reno = { .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, }; - -/* Initial congestion control used (until SYN) - * really reno under another name so we can tell difference - * during tcp_set_default_congestion_control - */ -struct tcp_congestion_ops tcp_init_congestion_ops = { - .name = "", - .owner = THIS_MODULE, - .ssthresh = tcp_reno_ssthresh, - .cong_avoid = tcp_reno_cong_avoid, -}; -EXPORT_SYMBOL_GPL(tcp_init_congestion_ops); -- cgit v1.2.3