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Date: Thu, 30 Aug 2012 16:39:07 -0700
From: "H.K. Jerry Chu" <hkchu@...gle.com>
To: davem@...emloft.net, ycheng@...gle.com, edumazet@...gle.com,
ncardwell@...gle.com
Cc: sivasankar@...ucsd.edu, therbert@...gle.com,
netdev@...r.kernel.org, Jerry Chu <hkchu@...gle.com>
Subject: [PATCH 2/3] tcp: TCP Fast Open Server - support TFO listeners
From: Jerry Chu <hkchu@...gle.com>
This patch builds on top of the previous patch to add the support
for TFO listeners. This includes -
1. allocating, properly initializing, and managing the per listener
fastopen_queue structure when TFO is enabled
2. changes to the inet_csk_accept code to support TFO. E.g., the
request_sock can no longer be freed upon accept(), not until 3WHS
finishes
3. allowing a TCP_SYN_RECV socket to properly poll() and sendmsg()
if it's a TFO socket
4. properly closing a TFO listener, and a TFO socket before 3WHS
finishes
5. supporting TCP_FASTOPEN socket option
6. modifying tcp_check_req() to use to check a TFO socket as well
as request_sock
7. supporting TCP's TFO cookie option
8. adding a new SYN-ACK retransmit handler to use the timer directly
off the TFO socket rather than the listener socket. Note that TFO
server side will not retransmit anything other than SYN-ACK until
the 3WHS is completed.
The patch also contains an important function
"reqsk_fastopen_remove()" to manage the somewhat complex relation
between a listener, its request_sock, and the corresponding child
socket. See the comment above the function for the detail.
Signed-off-by: H.K. Jerry Chu <hkchu@...gle.com>
Cc: Yuchung Cheng <ycheng@...gle.com>
Cc: Neal Cardwell <ncardwell@...gle.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Tom Herbert <therbert@...gle.com>
---
include/net/request_sock.h | 13 -----
include/net/tcp.h | 6 ++-
net/core/request_sock.c | 95 +++++++++++++++++++++++++++++++++++++++
net/ipv4/af_inet.c | 28 +++++++++++-
net/ipv4/inet_connection_sock.c | 57 +++++++++++++++++++++---
net/ipv4/syncookies.c | 1 +
net/ipv4/tcp.c | 49 +++++++++++++++++---
net/ipv4/tcp_ipv4.c | 4 +-
net/ipv4/tcp_minisocks.c | 61 ++++++++++++++++++++-----
net/ipv4/tcp_output.c | 21 +++++++--
net/ipv4/tcp_timer.c | 39 +++++++++++++++-
net/ipv6/syncookies.c | 1 +
net/ipv6/tcp_ipv6.c | 5 +-
13 files changed, 330 insertions(+), 50 deletions(-)
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index c3cdd6c..b01d8dd 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -226,19 +226,6 @@ static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue
return req;
}
-static inline struct sock *reqsk_queue_get_child(struct request_sock_queue *queue,
- struct sock *parent)
-{
- struct request_sock *req = reqsk_queue_remove(queue);
- struct sock *child = req->sk;
-
- WARN_ON(child == NULL);
-
- sk_acceptq_removed(parent);
- __reqsk_free(req);
- return child;
-}
-
static inline int reqsk_queue_removed(struct request_sock_queue *queue,
struct request_sock *req)
{
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1a88a97..2d1f70c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -414,7 +414,8 @@ extern enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *
const struct tcphdr *th);
extern struct sock * tcp_check_req(struct sock *sk,struct sk_buff *skb,
struct request_sock *req,
- struct request_sock **prev);
+ struct request_sock **prev,
+ bool fastopen);
extern int tcp_child_process(struct sock *parent, struct sock *child,
struct sk_buff *skb);
extern bool tcp_use_frto(struct sock *sk);
@@ -468,7 +469,8 @@ extern int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
extern int tcp_connect(struct sock *sk);
extern struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
struct request_sock *req,
- struct request_values *rvp);
+ struct request_values *rvp,
+ struct tcp_fastopen_cookie *foc);
extern int tcp_disconnect(struct sock *sk, int flags);
void tcp_connect_init(struct sock *sk);
diff --git a/net/core/request_sock.c b/net/core/request_sock.c
index 9b570a6..c31d9e8 100644
--- a/net/core/request_sock.c
+++ b/net/core/request_sock.c
@@ -15,6 +15,7 @@
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/string.h>
+#include <linux/tcp.h>
#include <linux/vmalloc.h>
#include <net/request_sock.h>
@@ -130,3 +131,97 @@ void reqsk_queue_destroy(struct request_sock_queue *queue)
kfree(lopt);
}
+/*
+ * This function is called to set a Fast Open socket's "fastopen_rsk" field
+ * to NULL when a TFO socket no longer needs to access the request_sock.
+ * This happens only after 3WHS has been either completed or aborted (e.g.,
+ * RST is received).
+ *
+ * Before TFO, a child socket is created only after 3WHS is completed,
+ * hence it never needs to access the request_sock. things get a lot more
+ * complex with TFO. A child socket, accepted or not, has to access its
+ * request_sock for 3WHS processing, e.g., to retransmit SYN-ACK pkts,
+ * until 3WHS is either completed or aborted. Afterwards the req will stay
+ * until either the child socket is accepted, or in the rare case when the
+ * listener is closed before the child is accepted.
+ *
+ * In short, a request socket is only freed after BOTH 3WHS has completed
+ * (or aborted) and the child socket has been accepted (or listener closed).
+ * When a child socket is accepted, its corresponding req->sk is set to
+ * NULL since it's no longer needed. More importantly, "req->sk == NULL"
+ * will be used by the code below to determine if a child socket has been
+ * accepted or not, and the check is protected by the fastopenq->lock
+ * described below.
+ *
+ * Note that fastopen_rsk is only accessed from the child socket's context
+ * with its socket lock held. But a request_sock (req) can be accessed by
+ * both its child socket through fastopen_rsk, and a listener socket through
+ * icsk_accept_queue.rskq_accept_head. To protect the access a simple spin
+ * lock per listener "icsk->icsk_accept_queue.fastopenq->lock" is created.
+ * only in the rare case when both the listener and the child locks are held,
+ * e.g., in inet_csk_listen_stop() do we not need to acquire the lock.
+ * The lock also protects other fields such as fastopenq->qlen, which is
+ * decremented by this function when fastopen_rsk is no longer needed.
+ *
+ * Note that another solution was to simply use the existing socket lock
+ * from the listener. But first socket lock is difficult to use. It is not
+ * a simple spin lock - one must consider sock_owned_by_user() and arrange
+ * to use sk_add_backlog() stuff. But what really makes it infeasible is the
+ * locking hierarchy violation. E.g., inet_csk_listen_stop() may try to
+ * acquire a child's lock while holding listener's socket lock. A corner
+ * case might also exist in tcp_v4_hnd_req() that will trigger this locking
+ * order.
+ *
+ * When a TFO req is created, it needs to sock_hold its listener to prevent
+ * the latter data structure from going away.
+ *
+ * This function also sets "treq->listener" to NULL and unreference listener
+ * socket. treq->listener is used by the listener so it is protected by the
+ * fastopenq->lock in this function.
+ */
+void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req,
+ bool reset)
+{
+ struct sock *lsk = tcp_rsk(req)->listener;
+ struct fastopen_queue *fastopenq =
+ inet_csk(lsk)->icsk_accept_queue.fastopenq;
+
+ BUG_ON(!spin_is_locked(&sk->sk_lock.slock) && !sock_owned_by_user(sk));
+
+ tcp_sk(sk)->fastopen_rsk = NULL;
+ spin_lock_bh(&fastopenq->lock);
+ fastopenq->qlen--;
+ tcp_rsk(req)->listener = NULL;
+ if (req->sk) /* the child socket hasn't been accepted yet */
+ goto out;
+
+ if (!reset || lsk->sk_state != TCP_LISTEN) {
+ /* If the listener has been closed don't bother with the
+ * special RST handling below.
+ */
+ spin_unlock_bh(&fastopenq->lock);
+ sock_put(lsk);
+ reqsk_free(req);
+ return;
+ }
+ /* Wait for 60secs before removing a req that has triggered RST.
+ * This is a simple defense against TFO spoofing attack - by
+ * counting the req against fastopen.max_qlen, and disabling
+ * TFO when the qlen exceeds max_qlen.
+ *
+ * For more details see CoNext'11 "TCP Fast Open" paper.
+ */
+ req->expires = jiffies + 60*HZ;
+ if (fastopenq->rskq_rst_head == NULL)
+ fastopenq->rskq_rst_head = req;
+ else
+ fastopenq->rskq_rst_tail->dl_next = req;
+
+ req->dl_next = NULL;
+ fastopenq->rskq_rst_tail = req;
+ fastopenq->qlen++;
+out:
+ spin_unlock_bh(&fastopenq->lock);
+ sock_put(lsk);
+ return;
+}
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 6681ccf..4f70ef0 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -149,6 +149,11 @@ void inet_sock_destruct(struct sock *sk)
pr_err("Attempt to release alive inet socket %p\n", sk);
return;
}
+ if (sk->sk_type == SOCK_STREAM) {
+ struct fastopen_queue *fastopenq =
+ inet_csk(sk)->icsk_accept_queue.fastopenq;
+ kfree(fastopenq);
+ }
WARN_ON(atomic_read(&sk->sk_rmem_alloc));
WARN_ON(atomic_read(&sk->sk_wmem_alloc));
@@ -212,6 +217,26 @@ int inet_listen(struct socket *sock, int backlog)
* we can only allow the backlog to be adjusted.
*/
if (old_state != TCP_LISTEN) {
+ /* Check special setups for testing purpose to enable TFO w/o
+ * requiring TCP_FASTOPEN sockopt.
+ * Note that only TCP sockets (SOCK_STREAM) will reach here.
+ * Also fastopenq may already been allocated because this
+ * socket was in TCP_LISTEN state previously but was
+ * shutdown() (rather than close()).
+ */
+ if ((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) != 0 &&
+ inet_csk(sk)->icsk_accept_queue.fastopenq == NULL) {
+ if ((sysctl_tcp_fastopen & TFO_SERVER_WO_SOCKOPT1) != 0)
+ err = fastopen_init_queue(sk, backlog);
+ else if ((sysctl_tcp_fastopen &
+ TFO_SERVER_WO_SOCKOPT2) != 0)
+ err = fastopen_init_queue(sk,
+ ((uint)sysctl_tcp_fastopen) >> 16);
+ else
+ err = 0;
+ if (err)
+ goto out;
+ }
err = inet_csk_listen_start(sk, backlog);
if (err)
goto out;
@@ -701,7 +726,8 @@ int inet_accept(struct socket *sock, struct socket *newsock, int flags)
sock_rps_record_flow(sk2);
WARN_ON(!((1 << sk2->sk_state) &
- (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT | TCPF_CLOSE)));
+ (TCPF_ESTABLISHED | TCPF_SYN_RECV |
+ TCPF_CLOSE_WAIT | TCPF_CLOSE)));
sock_graft(sk2, newsock);
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 7f75f21..8464b79 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -283,7 +283,9 @@ static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
{
struct inet_connection_sock *icsk = inet_csk(sk);
+ struct request_sock_queue *queue = &icsk->icsk_accept_queue;
struct sock *newsk;
+ struct request_sock *req;
int error;
lock_sock(sk);
@@ -296,7 +298,7 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
goto out_err;
/* Find already established connection */
- if (reqsk_queue_empty(&icsk->icsk_accept_queue)) {
+ if (reqsk_queue_empty(queue)) {
long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);
/* If this is a non blocking socket don't sleep */
@@ -308,14 +310,32 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
if (error)
goto out_err;
}
-
- newsk = reqsk_queue_get_child(&icsk->icsk_accept_queue, sk);
- WARN_ON(newsk->sk_state == TCP_SYN_RECV);
+ req = reqsk_queue_remove(queue);
+ newsk = req->sk;
+
+ sk_acceptq_removed(sk);
+ if (sk->sk_type == SOCK_STREAM && queue->fastopenq != NULL) {
+ spin_lock_bh(&queue->fastopenq->lock);
+ if (tcp_rsk(req)->listener) {
+ /* We are still waiting for the final ACK from 3WHS
+ * so can't free req now. Instead, we set req->sk to
+ * NULL to signify that the child socket is taken
+ * so reqsk_fastopen_remove() will free the req
+ * when 3WHS finishes (or is aborted).
+ */
+ req->sk = NULL;
+ req = NULL;
+ }
+ spin_unlock_bh(&queue->fastopenq->lock);
+ }
out:
release_sock(sk);
+ if (req)
+ __reqsk_free(req);
return newsk;
out_err:
newsk = NULL;
+ req = NULL;
*err = error;
goto out;
}
@@ -720,13 +740,14 @@ EXPORT_SYMBOL_GPL(inet_csk_listen_start);
void inet_csk_listen_stop(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
+ struct request_sock_queue *queue = &icsk->icsk_accept_queue;
struct request_sock *acc_req;
struct request_sock *req;
inet_csk_delete_keepalive_timer(sk);
/* make all the listen_opt local to us */
- acc_req = reqsk_queue_yank_acceptq(&icsk->icsk_accept_queue);
+ acc_req = reqsk_queue_yank_acceptq(queue);
/* Following specs, it would be better either to send FIN
* (and enter FIN-WAIT-1, it is normal close)
@@ -736,7 +757,7 @@ void inet_csk_listen_stop(struct sock *sk)
* To be honest, we are not able to make either
* of the variants now. --ANK
*/
- reqsk_queue_destroy(&icsk->icsk_accept_queue);
+ reqsk_queue_destroy(queue);
while ((req = acc_req) != NULL) {
struct sock *child = req->sk;
@@ -754,6 +775,19 @@ void inet_csk_listen_stop(struct sock *sk)
percpu_counter_inc(sk->sk_prot->orphan_count);
+ if (sk->sk_type == SOCK_STREAM && tcp_rsk(req)->listener) {
+ BUG_ON(tcp_sk(child)->fastopen_rsk != req);
+ BUG_ON(sk != tcp_rsk(req)->listener);
+
+ /* Paranoid, to prevent race condition if
+ * an inbound pkt destined for child is
+ * blocked by sock lock in tcp_v4_rcv().
+ * Also to satisfy an assertion in
+ * tcp_v4_destroy_sock().
+ */
+ tcp_sk(child)->fastopen_rsk = NULL;
+ sock_put(sk);
+ }
inet_csk_destroy_sock(child);
bh_unlock_sock(child);
@@ -763,6 +797,17 @@ void inet_csk_listen_stop(struct sock *sk)
sk_acceptq_removed(sk);
__reqsk_free(req);
}
+ if (queue->fastopenq != NULL) {
+ /* Free all the reqs queued in rskq_rst_head. */
+ spin_lock_bh(&queue->fastopenq->lock);
+ acc_req = queue->fastopenq->rskq_rst_head;
+ queue->fastopenq->rskq_rst_head = NULL;
+ spin_unlock_bh(&queue->fastopenq->lock);
+ while ((req = acc_req) != NULL) {
+ acc_req = req->dl_next;
+ __reqsk_free(req);
+ }
+ }
WARN_ON(sk->sk_ack_backlog);
}
EXPORT_SYMBOL_GPL(inet_csk_listen_stop);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 650e152..ba48e79 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -319,6 +319,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
ireq->tstamp_ok = tcp_opt.saw_tstamp;
req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
treq->snt_synack = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsecr : 0;
+ treq->listener = NULL;
/* We throwed the options of the initial SYN away, so we hope
* the ACK carries the same options again (see RFC1122 4.2.3.8)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2109ff4..df83d74 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -486,8 +486,9 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
if (sk->sk_shutdown & RCV_SHUTDOWN)
mask |= POLLIN | POLLRDNORM | POLLRDHUP;
- /* Connected? */
- if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV)) {
+ /* Connected or passive Fast Open socket? */
+ if (sk->sk_state != TCP_SYN_SENT &&
+ (sk->sk_state != TCP_SYN_RECV || tp->fastopen_rsk != NULL)) {
int target = sock_rcvlowat(sk, 0, INT_MAX);
if (tp->urg_seq == tp->copied_seq &&
@@ -840,10 +841,15 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffse
ssize_t copied;
long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
- /* Wait for a connection to finish. */
- if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
+ /* Wait for a connection to finish. One exception is TCP Fast Open
+ * (passive side) where data is allowed to be sent before a connection
+ * is fully established.
+ */
+ if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
+ !tcp_passive_fastopen(sk)) {
if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
goto out_err;
+ }
clear_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags);
@@ -1042,10 +1048,15 @@ int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
- /* Wait for a connection to finish. */
- if ((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
+ /* Wait for a connection to finish. One exception is TCP Fast Open
+ * (passive side) where data is allowed to be sent before a connection
+ * is fully established.
+ */
+ if (((1 << sk->sk_state) & ~(TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) &&
+ !tcp_passive_fastopen(sk)) {
if ((err = sk_stream_wait_connect(sk, &timeo)) != 0)
goto do_error;
+ }
if (unlikely(tp->repair)) {
if (tp->repair_queue == TCP_RECV_QUEUE) {
@@ -2144,6 +2155,10 @@ void tcp_close(struct sock *sk, long timeout)
* they look as CLOSING or LAST_ACK for Linux)
* Probably, I missed some more holelets.
* --ANK
+ * XXX (TFO) - To start off we don't support SYN+ACK+FIN
+ * in a single packet! (May consider it later but will
+ * probably need API support or TCP_CORK SYN-ACK until
+ * data is written and socket is closed.)
*/
tcp_send_fin(sk);
}
@@ -2215,8 +2230,16 @@ adjudge_to_death:
}
}
- if (sk->sk_state == TCP_CLOSE)
+ if (sk->sk_state == TCP_CLOSE) {
+ struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+ /* We could get here with a non-NULL req if the socket is
+ * aborted (e.g., closed with unread data) before 3WHS
+ * finishes.
+ */
+ if (req != NULL)
+ reqsk_fastopen_remove(sk, req, false);
inet_csk_destroy_sock(sk);
+ }
/* Otherwise, socket is reprieved until protocol close. */
out:
@@ -2688,6 +2711,14 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
else
icsk->icsk_user_timeout = msecs_to_jiffies(val);
break;
+
+ case TCP_FASTOPEN:
+ if (val >= 0 && ((1 << sk->sk_state) & (TCPF_CLOSE |
+ TCPF_LISTEN)))
+ err = fastopen_init_queue(sk, val);
+ else
+ err = -EINVAL;
+ break;
default:
err = -ENOPROTOOPT;
break;
@@ -3501,11 +3532,15 @@ EXPORT_SYMBOL(tcp_cookie_generator);
void tcp_done(struct sock *sk)
{
+ struct request_sock *req = tcp_sk(sk)->fastopen_rsk;
+
if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
tcp_set_state(sk, TCP_CLOSE);
tcp_clear_xmit_timers(sk);
+ if (req != NULL)
+ reqsk_fastopen_remove(sk, req, false);
sk->sk_shutdown = SHUTDOWN_MASK;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 36f02f9..bb148de 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -839,7 +839,7 @@ 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, rvp);
+ skb = tcp_make_synack(sk, dst, req, rvp, NULL);
if (skb) {
__tcp_v4_send_check(skb, ireq->loc_addr, ireq->rmt_addr);
@@ -1554,7 +1554,7 @@ static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
struct request_sock *req = inet_csk_search_req(sk, &prev, th->source,
iph->saddr, iph->daddr);
if (req)
- return tcp_check_req(sk, skb, req, prev);
+ return tcp_check_req(sk, skb, req, prev, false);
nsk = inet_lookup_established(sock_net(sk), &tcp_hashinfo, iph->saddr,
th->source, iph->daddr, th->dest, inet_iif(skb));
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 6ff7f10..e965319 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -507,6 +507,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;
newtp->rx_opt.mss_clamp = req->mss;
TCP_ECN_openreq_child(newtp, req);
+ newtp->fastopen_rsk = NULL;
TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_PASSIVEOPENS);
}
@@ -515,13 +516,18 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
EXPORT_SYMBOL(tcp_create_openreq_child);
/*
- * Process an incoming packet for SYN_RECV sockets represented
- * as a request_sock.
+ * Process an incoming packet for SYN_RECV sockets represented as a
+ * request_sock. Normally sk is the listener socket but for TFO it
+ * points to the child socket.
+ *
+ * XXX (TFO) - The current impl contains a special check for ack
+ * validation and inside tcp_v4_reqsk_send_ack(). Can we do better?
*/
struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
- struct request_sock **prev)
+ struct request_sock **prev,
+ bool fastopen)
{
struct tcp_options_received tmp_opt;
const u8 *hash_location;
@@ -530,6 +536,8 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
__be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
bool paws_reject = false;
+ BUG_ON(fastopen == (sk->sk_state == TCP_LISTEN));
+
tmp_opt.saw_tstamp = 0;
if (th->doff > (sizeof(struct tcphdr)>>2)) {
tcp_parse_options(skb, &tmp_opt, &hash_location, 0, NULL);
@@ -565,6 +573,9 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
*
* Enforce "SYN-ACK" according to figure 8, figure 6
* of RFC793, fixed by RFC1122.
+ *
+ * Note that even if there is new data in the SYN packet
+ * they will be thrown away too.
*/
req->rsk_ops->rtx_syn_ack(sk, req, NULL);
return NULL;
@@ -622,9 +633,12 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
* sent (the segment carries an unacceptable ACK) ...
* a reset is sent."
*
- * Invalid ACK: reset will be sent by listening socket
+ * Invalid ACK: reset will be sent by listening socket.
+ * Note that the ACK validity check for a Fast Open socket is done
+ * elsewhere and is checked directly against the child socket rather
+ * than req because user data may have been sent out.
*/
- if ((flg & TCP_FLAG_ACK) &&
+ if ((flg & TCP_FLAG_ACK) && !fastopen &&
(TCP_SKB_CB(skb)->ack_seq !=
tcp_rsk(req)->snt_isn + 1 + tcp_s_data_size(tcp_sk(sk))))
return sk;
@@ -637,7 +651,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
/* RFC793: "first check sequence number". */
if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
- tcp_rsk(req)->rcv_isn + 1, tcp_rsk(req)->rcv_isn + 1 + req->rcv_wnd)) {
+ tcp_rsk(req)->rcv_nxt, tcp_rsk(req)->rcv_nxt + req->rcv_wnd)) {
/* Out of window: send ACK and drop. */
if (!(flg & TCP_FLAG_RST))
req->rsk_ops->send_ack(sk, skb, req);
@@ -648,7 +662,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
/* In sequence, PAWS is OK. */
- if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_isn + 1))
+ if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_nxt))
req->ts_recent = tmp_opt.rcv_tsval;
if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
@@ -667,10 +681,19 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
/* ACK sequence verified above, just make sure ACK is
* set. If ACK not set, just silently drop the packet.
+ *
+ * XXX (TFO) - if we ever allow "data after SYN", the
+ * following check needs to be removed.
*/
if (!(flg & TCP_FLAG_ACK))
return NULL;
+ /* For Fast Open no more processing is needed (sk is the
+ * child socket).
+ */
+ if (fastopen)
+ return sk;
+
/* While TCP_DEFER_ACCEPT is active, drop bare ACK. */
if (req->retrans < inet_csk(sk)->icsk_accept_queue.rskq_defer_accept &&
TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
@@ -706,11 +729,21 @@ listen_overflow:
}
embryonic_reset:
- NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_EMBRYONICRSTS);
- if (!(flg & TCP_FLAG_RST))
+ if (!(flg & TCP_FLAG_RST)) {
+ /* Received a bad SYN pkt - for TFO We try not to reset
+ * the local connection unless it's really necessary to
+ * avoid becoming vulnerable to outside attack aiming at
+ * resetting legit local connections.
+ */
req->rsk_ops->send_reset(sk, skb);
-
- inet_csk_reqsk_queue_drop(sk, req, prev);
+ } else if (fastopen) { /* received a valid RST pkt */
+ reqsk_fastopen_remove(sk, req, true);
+ tcp_reset(sk);
+ }
+ if (!fastopen) {
+ inet_csk_reqsk_queue_drop(sk, req, prev);
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_EMBRYONICRSTS);
+ }
return NULL;
}
EXPORT_SYMBOL(tcp_check_req);
@@ -719,6 +752,12 @@ EXPORT_SYMBOL(tcp_check_req);
* Queue segment on the new socket if the new socket is active,
* otherwise we just shortcircuit this and continue with
* the new socket.
+ *
+ * For the vast majority of cases child->sk_state will be TCP_SYN_RECV
+ * when entering. But other states are possible due to a race condition
+ * where after __inet_lookup_established() fails but before the listener
+ * locked is obtained, other packets cause the same connection to
+ * be created.
*/
int tcp_child_process(struct sock *parent, struct sock *child,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d046326..9383b51 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -702,7 +702,8 @@ static unsigned int tcp_synack_options(struct sock *sk,
unsigned int mss, struct sk_buff *skb,
struct tcp_out_options *opts,
struct tcp_md5sig_key **md5,
- struct tcp_extend_values *xvp)
+ struct tcp_extend_values *xvp,
+ struct tcp_fastopen_cookie *foc)
{
struct inet_request_sock *ireq = inet_rsk(req);
unsigned int remaining = MAX_TCP_OPTION_SPACE;
@@ -747,7 +748,15 @@ static unsigned int tcp_synack_options(struct sock *sk,
if (unlikely(!ireq->tstamp_ok))
remaining -= TCPOLEN_SACKPERM_ALIGNED;
}
-
+ if (foc != NULL) {
+ u32 need = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
+ need = (need + 3) & ~3U; /* Align to 32 bits */
+ if (remaining >= need) {
+ opts->options |= OPTION_FAST_OPEN_COOKIE;
+ opts->fastopen_cookie = foc;
+ remaining -= need;
+ }
+ }
/* Similar rationale to tcp_syn_options() applies here, too.
* If the <SYN> options fit, the same options should fit now!
*/
@@ -2658,7 +2667,8 @@ int tcp_send_synack(struct sock *sk)
*/
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
struct request_sock *req,
- struct request_values *rvp)
+ struct request_values *rvp,
+ struct tcp_fastopen_cookie *foc)
{
struct tcp_out_options opts;
struct tcp_extend_values *xvp = tcp_xv(rvp);
@@ -2718,7 +2728,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
#endif
TCP_SKB_CB(skb)->when = tcp_time_stamp;
tcp_header_size = tcp_synack_options(sk, req, mss,
- skb, &opts, &md5, xvp)
+ skb, &opts, &md5, xvp, foc)
+ sizeof(*th);
skb_push(skb, tcp_header_size);
@@ -2772,7 +2782,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
}
th->seq = htonl(TCP_SKB_CB(skb)->seq);
- th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
+ /* XXX data is queued and acked as is. No buffer/window check */
+ th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt);
/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
th->window = htons(min(req->rcv_wnd, 65535U));
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index b774a03..fc04711 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -305,6 +305,35 @@ static void tcp_probe_timer(struct sock *sk)
}
/*
+ * Timer for Fast Open socket to retransmit SYNACK. Note that the
+ * sk here is the child socket, not the parent (listener) socket.
+ */
+static void tcp_fastopen_synack_timer(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ int max_retries = icsk->icsk_syn_retries ? :
+ sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */
+ struct request_sock *req;
+
+ req = tcp_sk(sk)->fastopen_rsk;
+ req->rsk_ops->syn_ack_timeout(sk, req);
+
+ if (req->retrans >= max_retries) {
+ tcp_write_err(sk);
+ return;
+ }
+ /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error
+ * returned from rtx_syn_ack() to make it more persistent like
+ * regular retransmit because if the child socket has been accepted
+ * it's not good to give up too easily.
+ */
+ req->rsk_ops->rtx_syn_ack(sk, req, NULL);
+ req->retrans++;
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+ TCP_TIMEOUT_INIT << req->retrans, TCP_RTO_MAX);
+}
+
+/*
* The TCP retransmit timer.
*/
@@ -317,7 +346,15 @@ void tcp_retransmit_timer(struct sock *sk)
tcp_resume_early_retransmit(sk);
return;
}
-
+ if (tp->fastopen_rsk) {
+ BUG_ON(sk->sk_state != TCP_SYN_RECV &&
+ sk->sk_state != TCP_FIN_WAIT1);
+ tcp_fastopen_synack_timer(sk);
+ /* Before we receive ACK to our SYN-ACK don't retransmit
+ * anything else (e.g., data or FIN segments).
+ */
+ return;
+ }
if (!tp->packets_out)
goto out;
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index bb46061..182ab9a 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -190,6 +190,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
ireq = inet_rsk(req);
ireq6 = inet6_rsk(req);
treq = tcp_rsk(req);
+ treq->listener = NULL;
if (security_inet_conn_request(sk, skb, req))
goto out_free;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index f99b81d..09078b9 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -475,7 +475,7 @@ static int tcp_v6_send_synack(struct sock *sk, struct dst_entry *dst,
if (!dst && (dst = inet6_csk_route_req(sk, fl6, req)) == NULL)
goto done;
- skb = tcp_make_synack(sk, dst, req, rvp);
+ skb = tcp_make_synack(sk, dst, req, rvp, NULL);
if (skb) {
__tcp_v6_send_check(skb, &treq->loc_addr, &treq->rmt_addr);
@@ -987,7 +987,7 @@ static struct sock *tcp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)
&ipv6_hdr(skb)->saddr,
&ipv6_hdr(skb)->daddr, inet6_iif(skb));
if (req)
- return tcp_check_req(sk, skb, req, prev);
+ return tcp_check_req(sk, skb, req, prev, false);
nsk = __inet6_lookup_established(sock_net(sk), &tcp_hashinfo,
&ipv6_hdr(skb)->saddr, th->source,
@@ -1179,6 +1179,7 @@ have_isn:
want_cookie)
goto drop_and_free;
+ tcp_rsk(req)->listener = NULL;
inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
return 0;
--
1.7.7.3
--
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