From 843f4a55e336e6d0c7bb92e7f9621535bc8d5fcd Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Sun, 11 May 2014 20:22:11 -0700 Subject: [PATCH] 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 Signed-off-by: Daniel Lee Signed-off-by: Jerry Chu Acked-by: Neal Cardwell Signed-off-by: David S. Miller --- include/net/tcp.h | 14 ++++----- net/ipv4/tcp_fastopen.c | 67 +++++++++++++++++++--------------------- net/ipv4/tcp_ipv4.c | 57 ++++++++++------------------------ net/ipv4/tcp_minisocks.c | 31 +++++++++++++++++++ net/ipv4/tcp_output.c | 21 ------------- 5 files changed, 85 insertions(+), 105 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 17d7c6a3d037..f5d6ca4a9d28 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1114,6 +1114,9 @@ static inline void tcp_openreq_init(struct request_sock *req, ireq->ir_num = ntohs(tcp_hdr(skb)->dest); } +extern void tcp_openreq_init_rwin(struct request_sock *req, + struct sock *sk, struct dst_entry *dst); + void tcp_enter_memory_pressure(struct sock *sk); static inline int keepalive_intvl_when(const struct tcp_sock *tp) @@ -1323,13 +1326,10 @@ void tcp_free_fastopen_req(struct tcp_sock *tp); extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx; int tcp_fastopen_reset_cipher(void *key, unsigned int len); -int tcp_fastopen_create_child(struct sock *sk, - struct sk_buff *skb, - struct sk_buff *skb_synack, - struct request_sock *req); -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); void tcp_fastopen_init_key_once(bool publish); #define TCP_FASTOPEN_KEY_LENGTH 16 diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c index 5a98277b9a82..9b947a9aaf6e 100644 --- a/net/ipv4/tcp_fastopen.c +++ b/net/ipv4/tcp_fastopen.c @@ -95,34 +95,22 @@ void tcp_fastopen_cookie_gen(__be32 src, __be32 dst, 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 @@ int tcp_fastopen_create_child(struct sock *sk, /* 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 @@ static bool tcp_fastopen_queue_check(struct sock *sk) * 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 @@ bool tcp_fastopen_check(struct sock *sk, struct sk_buff *skb, 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 @@ fastopen: *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 5ea0949dadfd..1665f0f84233 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -822,7 +822,8 @@ static void tcp_v4_reqsk_send_ack(struct sock *sk, struct sk_buff *skb, */ 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 @@ static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst, 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_send_synack(struct sock *sk, struct dst_entry *dst, 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 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) __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 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) 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 05c1b155251d..e68e0d4af6c9 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -362,6 +362,37 @@ void tcp_twsk_destructor(struct sock *sk) } 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 b20fc02920f9..3d61c52bdf79 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2803,27 +2803,6 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, 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)) -- 2.20.1