tcp: use tcp_v4_send_synack on first SYN-ACK
To avoid large code duplication in IPv6, we need to first simplify
the complicate SYN-ACK sending code in tcp_v4_conn_request().
To use tcp_v4(6)_send_synack() to send all SYN-ACKs, we need to
initialize the mini socket's receive window before trying to
create the child socket and/or building the SYN-ACK packet. So we move
that initialization from tcp_make_synack() to tcp_v4_conn_request()
as a new function tcp_openreq_init_req_rwin().
After this refactoring the SYN-ACK sending code is simpler and easier
to implement Fast Open for IPv6.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Daniel Lee <longinus00@gmail.com>
Signed-off-by: Jerry Chu <hkchu@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5ea0949..1665f0f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -822,7 +822,8 @@
*/
static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
struct request_sock *req,
- u16 queue_mapping)
+ u16 queue_mapping,
+ struct tcp_fastopen_cookie *foc)
{
const struct inet_request_sock *ireq = inet_rsk(req);
struct flowi4 fl4;
@@ -833,7 +834,7 @@
if (!dst && (dst = inet_csk_route_req(sk, &fl4, req)) == NULL)
return -1;
- skb = tcp_make_synack(sk, dst, req, NULL);
+ skb = tcp_make_synack(sk, dst, req, foc);
if (skb) {
__tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
@@ -852,7 +853,7 @@
static int tcp_v4_rtx_synack(struct sock *sk, struct request_sock *req)
{
- int res = tcp_v4_send_synack(sk, NULL, req, 0);
+ int res = tcp_v4_send_synack(sk, NULL, req, 0, NULL);
if (!res) {
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
@@ -1270,11 +1271,10 @@
__be32 saddr = ip_hdr(skb)->saddr;
__be32 daddr = ip_hdr(skb)->daddr;
__u32 isn = TCP_SKB_CB(skb)->when;
- bool want_cookie = false;
+ bool want_cookie = false, fastopen;
struct flowi4 fl4;
struct tcp_fastopen_cookie foc = { .len = -1 };
- struct sk_buff *skb_synack;
- int do_fastopen;
+ int err;
/* Never answer to SYNs send to broadcast or multicast */
if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
@@ -1373,49 +1373,24 @@
isn = tcp_v4_init_sequence(skb);
}
- tcp_rsk(req)->snt_isn = isn;
-
- if (dst == NULL) {
- dst = inet_csk_route_req(sk, &fl4, req);
- if (dst == NULL)
- goto drop_and_free;
- }
- do_fastopen = !want_cookie &&
- tcp_fastopen_check(sk, skb, req, &foc);
-
- /* We don't call tcp_v4_send_synack() directly because we need
- * to make sure a child socket can be created successfully before
- * sending back synack!
- *
- * XXX (TFO) - Ideally one would simply call tcp_v4_send_synack()
- * (or better yet, call tcp_send_synack() in the child context
- * directly, but will have to fix bunch of other code first)
- * after syn_recv_sock() except one will need to first fix the
- * latter to remove its dependency on the current implementation
- * of tcp_v4_send_synack()->tcp_select_initial_window().
- */
- skb_synack = tcp_make_synack(sk, dst, req, &foc);
-
- if (skb_synack) {
- __tcp_v4_send_check(skb_synack, ireq->ir_loc_addr, ireq->ir_rmt_addr);
- skb_set_queue_mapping(skb_synack, skb_get_queue_mapping(skb));
- } else
+ if (!dst && (dst = inet_csk_route_req(sk, &fl4, req)) == NULL)
goto drop_and_free;
- if (likely(!do_fastopen)) {
- int err;
- err = ip_build_and_send_pkt(skb_synack, sk, ireq->ir_loc_addr,
- ireq->ir_rmt_addr, ireq->opt);
- err = net_xmit_eval(err);
+ tcp_rsk(req)->snt_isn = isn;
+ tcp_rsk(req)->snt_synack = tcp_time_stamp;
+ tcp_openreq_init_rwin(req, sk, dst);
+ fastopen = !want_cookie &&
+ tcp_try_fastopen(sk, skb, req, &foc, dst);
+ err = tcp_v4_send_synack(sk, dst, req,
+ skb_get_queue_mapping(skb), &foc);
+ if (!fastopen) {
if (err || want_cookie)
goto drop_and_free;
tcp_rsk(req)->snt_synack = tcp_time_stamp;
tcp_rsk(req)->listener = NULL;
- /* Add the request_sock to the SYN table */
inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
- } else if (tcp_fastopen_create_child(sk, skb, skb_synack, req))
- goto drop_and_release;
+ }
return 0;
