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_fastopen.c b/net/ipv4/tcp_fastopen.c
index 5a98277..9b947a9 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -95,34 +95,22 @@
rcu_read_unlock();
}
-int tcp_fastopen_create_child(struct sock *sk,
- struct sk_buff *skb,
- struct sk_buff *skb_synack,
- struct request_sock *req)
+static bool tcp_fastopen_create_child(struct sock *sk,
+ struct sk_buff *skb,
+ struct dst_entry *dst,
+ struct request_sock *req)
{
struct tcp_sock *tp = tcp_sk(sk);
struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
- const struct inet_request_sock *ireq = inet_rsk(req);
struct sock *child;
- int err;
req->num_retrans = 0;
req->num_timeout = 0;
req->sk = NULL;
child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
- if (child == NULL) {
- NET_INC_STATS_BH(sock_net(sk),
- LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
- kfree_skb(skb_synack);
- return -1;
- }
- err = ip_build_and_send_pkt(skb_synack, sk, ireq->ir_loc_addr,
- ireq->ir_rmt_addr, ireq->opt);
- err = net_xmit_eval(err);
- if (!err)
- tcp_rsk(req)->snt_synack = tcp_time_stamp;
- /* XXX (TFO) - is it ok to ignore error and continue? */
+ if (child == NULL)
+ return false;
spin_lock(&queue->fastopenq->lock);
queue->fastopenq->qlen++;
@@ -167,28 +155,24 @@
/* Queue the data carried in the SYN packet. We need to first
* bump skb's refcnt because the caller will attempt to free it.
*
- * XXX (TFO) - we honor a zero-payload TFO request for now.
- * (Any reason not to?)
+ * XXX (TFO) - we honor a zero-payload TFO request for now,
+ * (any reason not to?) but no need to queue the skb since
+ * there is no data. How about SYN+FIN?
*/
- if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq + 1) {
- /* Don't queue the skb if there is no payload in SYN.
- * XXX (TFO) - How about SYN+FIN?
- */
- tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
- } else {
+ if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1) {
skb = skb_get(skb);
skb_dst_drop(skb);
__skb_pull(skb, tcp_hdr(skb)->doff * 4);
skb_set_owner_r(skb, child);
__skb_queue_tail(&child->sk_receive_queue, skb);
- tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
tp->syn_data_acked = 1;
}
+ tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
sk->sk_data_ready(sk);
bh_unlock_sock(child);
sock_put(child);
WARN_ON(req->sk == NULL);
- return 0;
+ return true;
}
EXPORT_SYMBOL(tcp_fastopen_create_child);
@@ -232,9 +216,10 @@
* may be updated and return the client in the SYN-ACK later. E.g., Fast Open
* cookie request (foc->len == 0).
*/
-bool tcp_fastopen_check(struct sock *sk, struct sk_buff *skb,
- struct request_sock *req,
- struct tcp_fastopen_cookie *foc)
+bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
+ struct request_sock *req,
+ struct tcp_fastopen_cookie *foc,
+ struct dst_entry *dst)
{
struct tcp_fastopen_cookie valid_foc = { .len = -1 };
bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
@@ -255,11 +240,21 @@
if (foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
foc->len == valid_foc.len &&
!memcmp(foc->val, valid_foc.val, foc->len)) {
+ /* Cookie is valid. Create a (full) child socket to accept
+ * the data in SYN before returning a SYN-ACK to ack the
+ * data. If we fail to create the socket, fall back and
+ * ack the ISN only but includes the same cookie.
+ *
+ * Note: Data-less SYN with valid cookie is allowed to send
+ * data in SYN_RECV state.
+ */
fastopen:
- tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
- foc->len = -1;
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVE);
- return true;
+ if (tcp_fastopen_create_child(sk, skb, dst, req)) {
+ foc->len = -1;
+ NET_INC_STATS_BH(sock_net(sk),
+ LINUX_MIB_TCPFASTOPENPASSIVE);
+ return true;
+ }
}
NET_INC_STATS_BH(sock_net(sk), foc->len ?
@@ -268,4 +263,4 @@
*foc = valid_foc;
return false;
}
-EXPORT_SYMBOL(tcp_fastopen_check);
+EXPORT_SYMBOL(tcp_try_fastopen);