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;