bpf: Add support for changing congestion control

Added support for changing congestion control for SOCK_OPS bpf
programs through the setsockopt bpf helper function. It also adds
a new SOCK_OPS op, BPF_SOCK_OPS_NEEDS_ECN, that is needed for
congestion controls, like dctcp, that need to enable ECN in the
SYN packets.

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 33b3e401e812..4d36f0b093e6 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -316,7 +316,8 @@ static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
         TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
         if (!(tp->ecn_flags & TCP_ECN_OK))
                 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
-        else if (tcp_ca_needs_ecn(sk))
+        else if (tcp_ca_needs_ecn(sk) ||
+                 tcp_bpf_ca_needs_ecn(sk))
                 INET_ECN_xmit(sk);
 }
 
@@ -324,8 +325,9 @@ static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
 static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
 {
         struct tcp_sock *tp = tcp_sk(sk);
+        bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
         bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
-                       tcp_ca_needs_ecn(sk);
+                tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
 
         if (!use_ecn) {
                 const struct dst_entry *dst = __sk_dst_get(sk);
@@ -339,7 +341,7 @@ static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
         if (use_ecn) {
                 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
                 tp->ecn_flags = TCP_ECN_OK;
-                if (tcp_ca_needs_ecn(sk))
+                if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
                         INET_ECN_xmit(sk);
         }
 }