Commit | Line | Data |
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a6503abf | 1 | /* tcp_output.c 4.18 81/11/25 */ |
76ee76df BJ |
2 | |
3 | #include "../h/param.h" | |
4 | #include "../h/systm.h" | |
5 | #include "../h/mbuf.h" | |
6 | #include "../h/socket.h" | |
d52566dd | 7 | #include "../h/socketvar.h" |
d52566dd | 8 | #include "../net/inet.h" |
53a5409e | 9 | #include "../net/inet_pcb.h" |
d52566dd BJ |
10 | #include "../net/inet_systm.h" |
11 | #include "../net/imp.h" | |
12 | #include "../net/ip.h" | |
eb44bfb2 | 13 | #include "../net/ip_var.h" |
d52566dd BJ |
14 | #include "../net/tcp.h" |
15 | #include "../net/tcp_var.h" | |
16 | #include "../net/tcp_fsm.h" | |
17 | #include "/usr/include/errno.h" | |
76ee76df | 18 | |
ea727f86 | 19 | /* |
a6503abf BJ |
20 | * Tcp output routine: figure out what should be sent |
21 | * and, if nothing, send a null segment anyways if force is nonzero | |
22 | * (e.g. to be sure to send an ACK). | |
23 | * | |
24 | * This routine can be called only after SYNs have been exchanged. | |
ea727f86 | 25 | */ |
a6503abf | 26 | tcp_output(tp) |
53a5409e | 27 | register struct tcpcb *tp; |
ea727f86 | 28 | { |
53a5409e | 29 | register struct socket *so = tp->t_inpcb->inp_socket; |
a6503abf BJ |
30 | register int len; |
31 | struct mbuf *m0; | |
32 | int off, flags; | |
33 | register struct mbuf *m; | |
34 | register struct tcpiphdr *ti; | |
35 | int win; | |
76ee76df | 36 | |
a6503abf | 37 | COUNT(TCP_OUTPUT); |
76ee76df | 38 | |
a6503abf BJ |
39 | /* |
40 | * Determine length of data that can be transmitted. | |
41 | * If will transmit to end of data and no more data | |
42 | * is coming, then send FIN also. | |
43 | * Make a copy of the data (if any). If no data | |
44 | * and not forced to transmit, just return. | |
45 | */ | |
46 | off = tp->snd_nxt - tp->snd_una; | |
47 | len = MIN(so->so_snd.sb_cc, tp->snd_wnd) - off; | |
48 | if (len > tp->mtu) | |
49 | len = tp->mtu; | |
50 | if (len == so->so_snd.sb_cc && (so->so_state & SS_CANTSNDMORE)) | |
51 | flags = TH_FIN; | |
52 | else | |
53 | flags = 0; | |
54 | if (len) | |
55 | goto send; | |
56 | ||
57 | /* | |
58 | * No data to send: see if something else makes us want to send. | |
59 | * First check if we owe peer and ack or have a unacked FIN to send. | |
60 | */ | |
61 | if (tp->t_flags & TF_OWEACK) | |
62 | goto send; | |
63 | if ((so->so_state & SS_CANTSNDMORE) && | |
64 | TCPS_OURFINISACKED(tp->t_state) == 0) | |
65 | goto send; | |
66 | if (tp->t_state == TCPS_SYN_SENT) { | |
67 | flags = TH_SYN; | |
68 | goto send; | |
76ee76df | 69 | } |
a6503abf BJ |
70 | if (tp->t_state == TCPS_CLOSED) { |
71 | flags = TH_RST; | |
72 | goto send; | |
76ee76df | 73 | } |
76ee76df | 74 | |
a6503abf BJ |
75 | /* |
76 | * Calculate available window in i, and also amount | |
77 | * of window known to peer (as advertised window less | |
78 | * next expected input.) If this is 35% or more of the | |
79 | * maximum possible window, then want to send a segment to peer. | |
80 | */ | |
81 | i = sbspace(&so->so_rcv) - tp->seqcnt; | |
82 | if (i > 0 && | |
83 | ((100*(i-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35)) | |
84 | goto send; | |
85 | ||
86 | /* | |
87 | * No reason to send a segment, just return. | |
88 | */ | |
89 | return; | |
90 | ||
91 | send: | |
92 | /* | |
93 | * Grab a header mbuf, attaching a copy of data to | |
94 | * be transmitted, and initialize the header from | |
95 | * the template for sends on this connection. | |
96 | */ | |
76ee76df BJ |
97 | MGET(m, 0); |
98 | if (m == 0) | |
99 | return (0); | |
53a5409e BJ |
100 | m->m_off = MMAXOFF - sizeof(struct tcpiphdr); |
101 | m->m_len = sizeof (struct tcpiphdr); | |
a6503abf BJ |
102 | if (len) { |
103 | m->m_next = m_copy(so->so_snd.sb_mb, off, len); | |
104 | if (m->m_next == 0) | |
105 | len = 0; | |
106 | } | |
107 | ti = mtod(m, struct tcpiphdr *); | |
108 | if (tp->t_template == 0) | |
109 | panic("tcp_output"); | |
110 | bcopy((caddr_t)tp->t_template, ti, sizeof (struct tcpiphdr)); | |
111 | ||
112 | /* | |
113 | * Fill in fields, remembering maximum advertised | |
114 | * window for use in delaying messages about window sizes. | |
115 | */ | |
116 | ti->ti_seq = htonl(tp->snd_nxt); | |
117 | ti->ti_ackno = htonl(tp->rcv_nxt); | |
118 | /* OPTIONS */ | |
76ee76df | 119 | if (flags & TH_SYN) |
a6503abf BJ |
120 | ti->ti_flags = flags; |
121 | else | |
122 | ti->ti_flags = flags | TH_ACK; | |
123 | win = sbspace(&so->so_rcv); | |
124 | if (win > 0) | |
125 | ti->ti_win = htons(win); | |
126 | if (SEQ_GT(tp->snd_urp, tp->snd_nxt)) | |
127 | ti->ti_urp = htons((u_short)(tp->snd_urp - tp->snd_nxt)); | |
128 | ti->ti_flags |= TH_URG; | |
129 | } else | |
130 | /* | |
131 | * If no urgent pointer to send, then we pull | |
132 | * the urgent pointer to the left edge of the send window | |
133 | * so that it doesn't drift into the send window on sequence | |
134 | * number wraparound. | |
135 | */ | |
136 | tp->snd_urp = tp->snd_una; /* drag it along */ | |
137 | ||
138 | /* | |
139 | * Put TCP length in extended header, and then | |
140 | * checksum extended header and data. | |
141 | */ | |
142 | if (len) | |
143 | ti->ti_len = htons((u_short)(len + sizeof (struct tcphdr))); | |
144 | ti->ti_sum = inet_cksum(m, sizeof (struct tcpiphdr) + len); | |
145 | ||
146 | /* | |
147 | * Fill in IP length and desired time to live and | |
148 | * send to IP level. | |
149 | */ | |
150 | ((struct ip *)ti)->ip_len = len + sizeof (struct tcpiphdr); | |
151 | ((struct ip *)ti)->ip_ttl = TCP_TTL; | |
152 | if (ip_output(m) == 0) | |
153 | return; | |
154 | ||
155 | /* | |
156 | * Data sent (as far as we can tell). | |
157 | * If this advertises a larger window than any other segment, | |
158 | * then record its sequence to be used in suppressing messages. | |
159 | * Advance snd_nxt to reflect transmitted sequence space, | |
160 | * drop send for purpose of ACK requirements, | |
161 | * and time transmission if not a retransmit. | |
162 | */ | |
163 | if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) | |
164 | tp->rcv_adv = tp->rcv_nxt + win; | |
165 | tp->snd_nxt += len; | |
166 | tp->t_flags &= ~(TF_OWEACK|TF_DELACK); | |
76ee76df | 167 | if (flags & TH_FIN) |
a6503abf BJ |
168 | tp->snd_nxt++; |
169 | if (SEQ_GT(tp->snd_nxt, tp->snd_hi)) { | |
170 | tp->snd_hi = tp->snd_nxt; | |
171 | /* TIME TRANSMIT */ | |
76ee76df | 172 | } |
a6503abf | 173 | return; |
76ee76df | 174 | } |