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);
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;
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 05c1b15..e68e0d4 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -362,6 +362,37 @@
}
EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
+void tcp_openreq_init_rwin(struct request_sock *req,
+ struct sock *sk, struct dst_entry *dst)
+{
+ struct inet_request_sock *ireq = inet_rsk(req);
+ struct tcp_sock *tp = tcp_sk(sk);
+ __u8 rcv_wscale;
+ int mss = dst_metric_advmss(dst);
+
+ if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
+ mss = tp->rx_opt.user_mss;
+
+ /* Set this up on the first call only */
+ req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
+
+ /* limit the window selection if the user enforce a smaller rx buffer */
+ if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+ (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
+ req->window_clamp = tcp_full_space(sk);
+
+ /* tcp_full_space because it is guaranteed to be the first packet */
+ tcp_select_initial_window(tcp_full_space(sk),
+ mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
+ &req->rcv_wnd,
+ &req->window_clamp,
+ ireq->wscale_ok,
+ &rcv_wscale,
+ dst_metric(dst, RTAX_INITRWND));
+ ireq->rcv_wscale = rcv_wscale;
+}
+EXPORT_SYMBOL(tcp_openreq_init_rwin);
+
static inline void TCP_ECN_openreq_child(struct tcp_sock *tp,
struct request_sock *req)
{
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b20fc02..3d61c52 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2803,27 +2803,6 @@
if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
mss = tp->rx_opt.user_mss;
- if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
- __u8 rcv_wscale;
- /* Set this up on the first call only */
- req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
-
- /* limit the window selection if the user enforce a smaller rx buffer */
- if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
- (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
- req->window_clamp = tcp_full_space(sk);
-
- /* tcp_full_space because it is guaranteed to be the first packet */
- tcp_select_initial_window(tcp_full_space(sk),
- mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
- &req->rcv_wnd,
- &req->window_clamp,
- ireq->wscale_ok,
- &rcv_wscale,
- dst_metric(dst, RTAX_INITRWND));
- ireq->rcv_wscale = rcv_wscale;
- }
-
memset(&opts, 0, sizeof(opts));
#ifdef CONFIG_SYN_COOKIES
if (unlikely(req->cookie_ts))