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tcp: use tcp_v4_send_synack on first SYN-ACK

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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>
This commit is contained in:
Yuchung Cheng 2014-05-11 20:22:11 -07:00 committed by David S. Miller
parent 89278c9dc9
commit 843f4a55e3
5 changed files with 85 additions and 105 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/net/tcp.h
View File

@ -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

67
net/ipv4/tcp_fastopen.c
View File

@ -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);

57
net/ipv4/tcp_ipv4.c
View File

@ -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;

31
net/ipv4/tcp_minisocks.c
View File

@ -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)
{

21
net/ipv4/tcp_output.c
View File

@ -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))