diff options
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 63 |
1 files changed, 47 insertions, 16 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index bd62712848fa..5200aab0ca97 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -59,6 +59,7 @@ int sysctl_tcp_base_mss __read_mostly = 512; /* By default, RFC2861 behavior. */ int sysctl_tcp_slow_start_after_idle __read_mostly = 1; +/* Account for new data that has been sent to the network. */ static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); @@ -142,6 +143,7 @@ static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst) tp->snd_cwnd_used = 0; } +/* Congestion state accounting after a packet has been sent. */ static void tcp_event_data_sent(struct tcp_sock *tp, struct sk_buff *skb, struct sock *sk) { @@ -161,6 +163,7 @@ static void tcp_event_data_sent(struct tcp_sock *tp, icsk->icsk_ack.pingpong = 1; } +/* Account for an ACK we sent. */ static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) { tcp_dec_quickack_mode(sk, pkts); @@ -276,6 +279,7 @@ static u16 tcp_select_window(struct sock *sk) return new_win; } +/* Packet ECN state for a SYN-ACK */ static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb) { TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_CWR; @@ -283,6 +287,7 @@ static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb) TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_ECE; } +/* Packet ECN state for a SYN. */ static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); @@ -301,6 +306,9 @@ TCP_ECN_make_synack(struct request_sock *req, struct tcphdr *th) th->ece = 1; } +/* Set up ECN state for a packet on a ESTABLISHED socket that is about to + * be sent. + */ static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb, int tcp_header_len) { @@ -362,7 +370,9 @@ struct tcp_out_options { __u32 tsval, tsecr; /* need to include OPTION_TS */ }; -/* Beware: Something in the Internet is very sensitive to the ordering of +/* Write previously computed TCP options to the packet. + * + * Beware: Something in the Internet is very sensitive to the ordering of * TCP options, we learned this through the hard way, so be careful here. * Luckily we can at least blame others for their non-compliance but from * inter-operatibility perspective it seems that we're somewhat stuck with @@ -445,6 +455,9 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, } } +/* Compute TCP options for SYN packets. This is not the final + * network wire format yet. + */ static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb, struct tcp_out_options *opts, struct tcp_md5sig_key **md5) { @@ -493,6 +506,7 @@ static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb, return size; } +/* Set up TCP options for SYN-ACKs. */ static unsigned tcp_synack_options(struct sock *sk, struct request_sock *req, unsigned mss, struct sk_buff *skb, @@ -541,6 +555,9 @@ static unsigned tcp_synack_options(struct sock *sk, return size; } +/* Compute TCP options for ESTABLISHED sockets. This is not the + * final wire format yet. + */ static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb, struct tcp_out_options *opts, struct tcp_md5sig_key **md5) { @@ -705,7 +722,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, return net_xmit_eval(err); } -/* This routine just queue's the buffer +/* This routine just queues the buffer for sending. * * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, * otherwise socket can stall. @@ -722,6 +739,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) sk_mem_charge(sk, skb->truesize); } +/* Initialize TSO segments for a packet. */ static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now) { @@ -909,6 +927,7 @@ static void __pskb_trim_head(struct sk_buff *skb, int len) skb->len = skb->data_len; } +/* Remove acked data from a packet in the transmit queue. */ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) { if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) @@ -937,7 +956,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) return 0; } -/* Not accounting for SACKs here. */ +/* Calculate MSS. Not accounting for SACKs here. */ int tcp_mtu_to_mss(struct sock *sk, int pmtu) { struct tcp_sock *tp = tcp_sk(sk); @@ -981,6 +1000,7 @@ int tcp_mss_to_mtu(struct sock *sk, int mss) return mtu; } +/* MTU probing init per socket */ void tcp_mtup_init(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); @@ -1143,7 +1163,8 @@ static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, return 0; } -/* This must be invoked the first time we consider transmitting +/* Intialize TSO state of a skb. + * This must be invoked the first time we consider transmitting * SKB onto the wire. */ static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, @@ -1158,6 +1179,7 @@ static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, return tso_segs; } +/* Minshall's variant of the Nagle send check. */ static inline int tcp_minshall_check(const struct tcp_sock *tp) { return after(tp->snd_sml, tp->snd_una) && @@ -1242,6 +1264,7 @@ static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb, return cwnd_quota; } +/* Test if sending is allowed right now. */ int tcp_may_send_now(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); @@ -1378,6 +1401,10 @@ send_now: } /* Create a new MTU probe if we are ready. + * MTU probe is regularly attempting to increase the path MTU by + * deliberately sending larger packets. This discovers routing + * changes resulting in larger path MTUs. + * * Returns 0 if we should wait to probe (no cwnd available), * 1 if a probe was sent, * -1 otherwise @@ -1790,6 +1817,7 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) sk_wmem_free_skb(sk, next_skb); } +/* Check if coalescing SKBs is legal. */ static int tcp_can_collapse(struct sock *sk, struct sk_buff *skb) { if (tcp_skb_pcount(skb) > 1) @@ -1808,6 +1836,9 @@ static int tcp_can_collapse(struct sock *sk, struct sk_buff *skb) return 1; } +/* Collapse packets in the retransmit queue to make to create + * less packets on the wire. This is only done on retransmission. + */ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, int space) { @@ -1957,6 +1988,9 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) return err; } +/* Check if we forward retransmits are possible in the current + * window/congestion state. + */ static int tcp_can_forward_retransmit(struct sock *sk) { const struct inet_connection_sock *icsk = inet_csk(sk); @@ -2101,7 +2135,8 @@ void tcp_send_fin(struct sock *sk) } else { /* Socket is locked, keep trying until memory is available. */ for (;;) { - skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL); + skb = alloc_skb_fclone(MAX_TCP_HEADER, + sk->sk_allocation); if (skb) break; yield(); @@ -2145,7 +2180,8 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority) TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS); } -/* WARNING: This routine must only be called when we have already sent +/* Send a crossed SYN-ACK during socket establishment. + * WARNING: This routine must only be called when we have already sent * a SYN packet that crossed the incoming SYN that caused this routine * to get called. If this assumption fails then the initial rcv_wnd * and rcv_wscale values will not be correct. @@ -2180,9 +2216,7 @@ int tcp_send_synack(struct sock *sk) return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); } -/* - * Prepare a SYN-ACK. - */ +/* Prepare a SYN-ACK. */ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, struct request_sock *req) { @@ -2269,9 +2303,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, return skb; } -/* - * Do all connect socket setups that can be done AF independent. - */ +/* Do all connect socket setups that can be done AF independent. */ static void tcp_connect_init(struct sock *sk) { struct dst_entry *dst = __sk_dst_get(sk); @@ -2330,9 +2362,7 @@ static void tcp_connect_init(struct sock *sk) tcp_clear_retrans(tp); } -/* - * Build a SYN and send it off. - */ +/* Build a SYN and send it off. */ int tcp_connect(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); @@ -2359,7 +2389,7 @@ int tcp_connect(struct sock *sk) sk->sk_wmem_queued += buff->truesize; sk_mem_charge(sk, buff->truesize); tp->packets_out += tcp_skb_pcount(buff); - tcp_transmit_skb(sk, buff, 1, GFP_KERNEL); + tcp_transmit_skb(sk, buff, 1, sk->sk_allocation); /* We change tp->snd_nxt after the tcp_transmit_skb() call * in order to make this packet get counted in tcpOutSegs. @@ -2493,6 +2523,7 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent) return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); } +/* Initiate keepalive or window probe from timer. */ int tcp_write_wakeup(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); |