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Diffstat (limited to 'net/ipv4/tcp_output.c')
-rw-r--r--net/ipv4/tcp_output.c343
1 files changed, 324 insertions, 19 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 803cbfe82fbc..33cd065cfbd8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -50,6 +50,9 @@ int sysctl_tcp_retrans_collapse __read_mostly = 1;
*/
int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
+/* Default TSQ limit of two TSO segments */
+int sysctl_tcp_limit_output_bytes __read_mostly = 131072;
+
/* This limits the percentage of the congestion window which we
* will allow a single TSO frame to consume. Building TSO frames
* which are too large can cause TCP streams to be bursty.
@@ -65,6 +68,8 @@ int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */
EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size);
+static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
+ int push_one, gfp_t gfp);
/* Account for new data that has been sent to the network. */
static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
@@ -380,15 +385,17 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)
#define OPTION_MD5 (1 << 2)
#define OPTION_WSCALE (1 << 3)
#define OPTION_COOKIE_EXTENSION (1 << 4)
+#define OPTION_FAST_OPEN_COOKIE (1 << 8)
struct tcp_out_options {
- u8 options; /* bit field of OPTION_* */
+ u16 options; /* bit field of OPTION_* */
+ u16 mss; /* 0 to disable */
u8 ws; /* window scale, 0 to disable */
u8 num_sack_blocks; /* number of SACK blocks to include */
u8 hash_size; /* bytes in hash_location */
- u16 mss; /* 0 to disable */
- __u32 tsval, tsecr; /* need to include OPTION_TS */
__u8 *hash_location; /* temporary pointer, overloaded */
+ __u32 tsval, tsecr; /* need to include OPTION_TS */
+ struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
};
/* The sysctl int routines are generic, so check consistency here.
@@ -437,7 +444,7 @@ static u8 tcp_cookie_size_check(u8 desired)
static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
struct tcp_out_options *opts)
{
- u8 options = opts->options; /* mungable copy */
+ u16 options = opts->options; /* mungable copy */
/* Having both authentication and cookies for security is redundant,
* and there's certainly not enough room. Instead, the cookie-less
@@ -559,6 +566,21 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
tp->rx_opt.dsack = 0;
}
+
+ if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) {
+ struct tcp_fastopen_cookie *foc = opts->fastopen_cookie;
+
+ *ptr++ = htonl((TCPOPT_EXP << 24) |
+ ((TCPOLEN_EXP_FASTOPEN_BASE + foc->len) << 16) |
+ TCPOPT_FASTOPEN_MAGIC);
+
+ memcpy(ptr, foc->val, foc->len);
+ if ((foc->len & 3) == 2) {
+ u8 *align = ((u8 *)ptr) + foc->len;
+ align[0] = align[1] = TCPOPT_NOP;
+ }
+ ptr += (foc->len + 3) >> 2;
+ }
}
/* Compute TCP options for SYN packets. This is not the final
@@ -574,6 +596,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ?
tcp_cookie_size_check(cvp->cookie_desired) :
0;
+ struct tcp_fastopen_request *fastopen = tp->fastopen_req;
#ifdef CONFIG_TCP_MD5SIG
*md5 = tp->af_specific->md5_lookup(sk, sk);
@@ -614,6 +637,16 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
remaining -= TCPOLEN_SACKPERM_ALIGNED;
}
+ if (fastopen && fastopen->cookie.len >= 0) {
+ u32 need = TCPOLEN_EXP_FASTOPEN_BASE + fastopen->cookie.len;
+ need = (need + 3) & ~3U; /* Align to 32 bits */
+ if (remaining >= need) {
+ opts->options |= OPTION_FAST_OPEN_COOKIE;
+ opts->fastopen_cookie = &fastopen->cookie;
+ remaining -= need;
+ tp->syn_fastopen = 1;
+ }
+ }
/* Note that timestamps are required by the specification.
*
* Odd numbers of bytes are prohibited by the specification, ensuring
@@ -783,6 +816,156 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
return size;
}
+
+/* TCP SMALL QUEUES (TSQ)
+ *
+ * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
+ * to reduce RTT and bufferbloat.
+ * We do this using a special skb destructor (tcp_wfree).
+ *
+ * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
+ * needs to be reallocated in a driver.
+ * The invariant being skb->truesize substracted from sk->sk_wmem_alloc
+ *
+ * Since transmit from skb destructor is forbidden, we use a tasklet
+ * to process all sockets that eventually need to send more skbs.
+ * We use one tasklet per cpu, with its own queue of sockets.
+ */
+struct tsq_tasklet {
+ struct tasklet_struct tasklet;
+ struct list_head head; /* queue of tcp sockets */
+};
+static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet);
+
+static void tcp_tsq_handler(struct sock *sk)
+{
+ if ((1 << sk->sk_state) &
+ (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING |
+ TCPF_CLOSE_WAIT | TCPF_LAST_ACK))
+ tcp_write_xmit(sk, tcp_current_mss(sk), 0, 0, GFP_ATOMIC);
+}
+/*
+ * One tasklest per cpu tries to send more skbs.
+ * We run in tasklet context but need to disable irqs when
+ * transfering tsq->head because tcp_wfree() might
+ * interrupt us (non NAPI drivers)
+ */
+static void tcp_tasklet_func(unsigned long data)
+{
+ struct tsq_tasklet *tsq = (struct tsq_tasklet *)data;
+ LIST_HEAD(list);
+ unsigned long flags;
+ struct list_head *q, *n;
+ struct tcp_sock *tp;
+ struct sock *sk;
+
+ local_irq_save(flags);
+ list_splice_init(&tsq->head, &list);
+ local_irq_restore(flags);
+
+ list_for_each_safe(q, n, &list) {
+ tp = list_entry(q, struct tcp_sock, tsq_node);
+ list_del(&tp->tsq_node);
+
+ sk = (struct sock *)tp;
+ bh_lock_sock(sk);
+
+ if (!sock_owned_by_user(sk)) {
+ tcp_tsq_handler(sk);
+ } else {
+ /* defer the work to tcp_release_cb() */
+ set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags);
+ }
+ bh_unlock_sock(sk);
+
+ clear_bit(TSQ_QUEUED, &tp->tsq_flags);
+ sk_free(sk);
+ }
+}
+
+#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
+ (1UL << TCP_WRITE_TIMER_DEFERRED) | \
+ (1UL << TCP_DELACK_TIMER_DEFERRED) | \
+ (1UL << TCP_MTU_REDUCED_DEFERRED))
+/**
+ * tcp_release_cb - tcp release_sock() callback
+ * @sk: socket
+ *
+ * called from release_sock() to perform protocol dependent
+ * actions before socket release.
+ */
+void tcp_release_cb(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ unsigned long flags, nflags;
+
+ /* perform an atomic operation only if at least one flag is set */
+ do {
+ flags = tp->tsq_flags;
+ if (!(flags & TCP_DEFERRED_ALL))
+ return;
+ nflags = flags & ~TCP_DEFERRED_ALL;
+ } while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags);
+
+ if (flags & (1UL << TCP_TSQ_DEFERRED))
+ tcp_tsq_handler(sk);
+
+ if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED))
+ tcp_write_timer_handler(sk);
+
+ if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED))
+ tcp_delack_timer_handler(sk);
+
+ if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED))
+ sk->sk_prot->mtu_reduced(sk);
+}
+EXPORT_SYMBOL(tcp_release_cb);
+
+void __init tcp_tasklet_init(void)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i);
+
+ INIT_LIST_HEAD(&tsq->head);
+ tasklet_init(&tsq->tasklet,
+ tcp_tasklet_func,
+ (unsigned long)tsq);
+ }
+}
+
+/*
+ * Write buffer destructor automatically called from kfree_skb.
+ * We cant xmit new skbs from this context, as we might already
+ * hold qdisc lock.
+ */
+void tcp_wfree(struct sk_buff *skb)
+{
+ struct sock *sk = skb->sk;
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) &&
+ !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
+ unsigned long flags;
+ struct tsq_tasklet *tsq;
+
+ /* Keep a ref on socket.
+ * This last ref will be released in tcp_tasklet_func()
+ */
+ atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc);
+
+ /* queue this socket to tasklet queue */
+ local_irq_save(flags);
+ tsq = &__get_cpu_var(tsq_tasklet);
+ list_add(&tp->tsq_node, &tsq->head);
+ tasklet_schedule(&tsq->tasklet);
+ local_irq_restore(flags);
+ } else {
+ sock_wfree(skb);
+ }
+}
+
/* This routine actually transmits TCP packets queued in by
* tcp_do_sendmsg(). This is used by both the initial
* transmission and possible later retransmissions.
@@ -844,7 +1027,12 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);
- skb_set_owner_w(skb, sk);
+
+ skb_orphan(skb);
+ skb->sk = sk;
+ skb->destructor = (sysctl_tcp_limit_output_bytes > 0) ?
+ tcp_wfree : sock_wfree;
+ atomic_add(skb->truesize, &sk->sk_wmem_alloc);
/* Build TCP header and checksum it. */
th = tcp_hdr(skb);
@@ -1780,6 +1968,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
while ((skb = tcp_send_head(sk))) {
unsigned int limit;
+
tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
BUG_ON(!tso_segs);
@@ -1800,6 +1989,13 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
break;
}
+ /* TSQ : sk_wmem_alloc accounts skb truesize,
+ * including skb overhead. But thats OK.
+ */
+ if (atomic_read(&sk->sk_wmem_alloc) >= sysctl_tcp_limit_output_bytes) {
+ set_bit(TSQ_THROTTLED, &tp->tsq_flags);
+ break;
+ }
limit = mss_now;
if (tso_segs > 1 && !tcp_urg_mode(tp))
limit = tcp_mss_split_point(sk, skb, mss_now,
@@ -2442,7 +2638,16 @@ int tcp_send_synack(struct sock *sk)
return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
}
-/* Prepare a SYN-ACK. */
+/**
+ * tcp_make_synack - Prepare a SYN-ACK.
+ * sk: listener socket
+ * dst: dst entry attached to the SYNACK
+ * req: request_sock pointer
+ * rvp: request_values pointer
+ *
+ * Allocate one skb and build a SYNACK packet.
+ * @dst is consumed : Caller should not use it again.
+ */
struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
struct request_sock *req,
struct request_values *rvp)
@@ -2461,14 +2666,15 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
if (cvp != NULL && cvp->s_data_constant && cvp->s_data_desired)
s_data_desired = cvp->s_data_desired;
- skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15 + s_data_desired, 1, GFP_ATOMIC);
- if (skb == NULL)
+ skb = alloc_skb(MAX_TCP_HEADER + 15 + s_data_desired, GFP_ATOMIC);
+ if (unlikely(!skb)) {
+ dst_release(dst);
return NULL;
-
+ }
/* Reserve space for headers. */
skb_reserve(skb, MAX_TCP_HEADER);
- skb_dst_set(skb, dst_clone(dst));
+ skb_dst_set(skb, dst);
mss = dst_metric_advmss(dst);
if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
@@ -2645,6 +2851,109 @@ void tcp_connect_init(struct sock *sk)
tcp_clear_retrans(tp);
}
+static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
+
+ tcb->end_seq += skb->len;
+ skb_header_release(skb);
+ __tcp_add_write_queue_tail(sk, skb);
+ sk->sk_wmem_queued += skb->truesize;
+ sk_mem_charge(sk, skb->truesize);
+ tp->write_seq = tcb->end_seq;
+ tp->packets_out += tcp_skb_pcount(skb);
+}
+
+/* Build and send a SYN with data and (cached) Fast Open cookie. However,
+ * queue a data-only packet after the regular SYN, such that regular SYNs
+ * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
+ * only the SYN sequence, the data are retransmitted in the first ACK.
+ * If cookie is not cached or other error occurs, falls back to send a
+ * regular SYN with Fast Open cookie request option.
+ */
+static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ struct tcp_fastopen_request *fo = tp->fastopen_req;
+ int syn_loss = 0, space, i, err = 0, iovlen = fo->data->msg_iovlen;
+ struct sk_buff *syn_data = NULL, *data;
+ unsigned long last_syn_loss = 0;
+
+ tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */
+ tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
+ &syn_loss, &last_syn_loss);
+ /* Recurring FO SYN losses: revert to regular handshake temporarily */
+ if (syn_loss > 1 &&
+ time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
+ fo->cookie.len = -1;
+ goto fallback;
+ }
+
+ if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE)
+ fo->cookie.len = -1;
+ else if (fo->cookie.len <= 0)
+ goto fallback;
+
+ /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
+ * user-MSS. Reserve maximum option space for middleboxes that add
+ * private TCP options. The cost is reduced data space in SYN :(
+ */
+ if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp)
+ tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
+ space = tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) -
+ MAX_TCP_OPTION_SPACE;
+
+ syn_data = skb_copy_expand(syn, skb_headroom(syn), space,
+ sk->sk_allocation);
+ if (syn_data == NULL)
+ goto fallback;
+
+ for (i = 0; i < iovlen && syn_data->len < space; ++i) {
+ struct iovec *iov = &fo->data->msg_iov[i];
+ unsigned char __user *from = iov->iov_base;
+ int len = iov->iov_len;
+
+ if (syn_data->len + len > space)
+ len = space - syn_data->len;
+ else if (i + 1 == iovlen)
+ /* No more data pending in inet_wait_for_connect() */
+ fo->data = NULL;
+
+ if (skb_add_data(syn_data, from, len))
+ goto fallback;
+ }
+
+ /* Queue a data-only packet after the regular SYN for retransmission */
+ data = pskb_copy(syn_data, sk->sk_allocation);
+ if (data == NULL)
+ goto fallback;
+ TCP_SKB_CB(data)->seq++;
+ TCP_SKB_CB(data)->tcp_flags &= ~TCPHDR_SYN;
+ TCP_SKB_CB(data)->tcp_flags = (TCPHDR_ACK|TCPHDR_PSH);
+ tcp_connect_queue_skb(sk, data);
+ fo->copied = data->len;
+
+ if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
+ tp->syn_data = (fo->copied > 0);
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
+ goto done;
+ }
+ syn_data = NULL;
+
+fallback:
+ /* Send a regular SYN with Fast Open cookie request option */
+ if (fo->cookie.len > 0)
+ fo->cookie.len = 0;
+ err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);
+ if (err)
+ tp->syn_fastopen = 0;
+ kfree_skb(syn_data);
+done:
+ fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */
+ return err;
+}
+
/* Build a SYN and send it off. */
int tcp_connect(struct sock *sk)
{
@@ -2662,17 +2971,13 @@ int tcp_connect(struct sock *sk)
skb_reserve(buff, MAX_TCP_HEADER);
tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
+ tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp;
+ tcp_connect_queue_skb(sk, buff);
TCP_ECN_send_syn(sk, buff);
- /* Send it off. */
- TCP_SKB_CB(buff)->when = tcp_time_stamp;
- tp->retrans_stamp = TCP_SKB_CB(buff)->when;
- skb_header_release(buff);
- __tcp_add_write_queue_tail(sk, buff);
- sk->sk_wmem_queued += buff->truesize;
- sk_mem_charge(sk, buff->truesize);
- tp->packets_out += tcp_skb_pcount(buff);
- err = tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
+ /* Send off SYN; include data in Fast Open. */
+ err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
+ tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
if (err == -ECONNREFUSED)
return err;
generated by cgit v1.2.3 (git 2.39.0) at 2024-11-19 23:48:10 +0300