diff options
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 343 |
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; |