Commit | Line | Data |
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4aed14e3 | 1 | /* tcp_output.c 4.22 81/12/12 */ |
76ee76df BJ |
2 | |
3 | #include "../h/param.h" | |
4 | #include "../h/systm.h" | |
5 | #include "../h/mbuf.h" | |
405c9168 | 6 | #include "../h/protosw.h" |
76ee76df | 7 | #include "../h/socket.h" |
d52566dd | 8 | #include "../h/socketvar.h" |
0974b45c BJ |
9 | #include "../net/in.h" |
10 | #include "../net/in_pcb.h" | |
11 | #include "../net/in_systm.h" | |
d52566dd | 12 | #include "../net/ip.h" |
eb44bfb2 | 13 | #include "../net/ip_var.h" |
d52566dd | 14 | #include "../net/tcp.h" |
0974b45c | 15 | #define TCPOUTFLAGS |
d52566dd | 16 | #include "../net/tcp_fsm.h" |
0974b45c BJ |
17 | #include "../net/tcp_seq.h" |
18 | #include "../net/tcp_timer.h" | |
19 | #include "../net/tcp_var.h" | |
20 | #include "../net/tcpip.h" | |
f1b2fa5b | 21 | #include "../errno.h" |
76ee76df | 22 | |
4aed14e3 | 23 | char *tcpstates[]; /* XXX */ |
ea727f86 | 24 | /* |
4aed14e3 | 25 | * Tcp output routine: figure out what should be sent and send it. |
ea727f86 | 26 | */ |
a6503abf | 27 | tcp_output(tp) |
53a5409e | 28 | register struct tcpcb *tp; |
ea727f86 | 29 | { |
53a5409e | 30 | register struct socket *so = tp->t_inpcb->inp_socket; |
a6503abf BJ |
31 | register int len; |
32 | struct mbuf *m0; | |
33 | int off, flags; | |
34 | register struct mbuf *m; | |
35 | register struct tcpiphdr *ti; | |
36 | int win; | |
76ee76df | 37 | |
a6503abf | 38 | COUNT(TCP_OUTPUT); |
76ee76df | 39 | |
a6503abf | 40 | /* |
0974b45c BJ |
41 | * Determine length of data that can be transmitted, |
42 | * and flags that will be used. | |
43 | * If there is some data or critical controls (SYN, RST) | |
44 | * to send, then transmit; otherwise, investigate further. | |
a6503abf BJ |
45 | */ |
46 | off = tp->snd_nxt - tp->snd_una; | |
405c9168 | 47 | len = MIN(so->so_snd.sb_cc, tp->snd_wnd+tp->t_force) - off; |
0974b45c BJ |
48 | if (len > tp->t_maxseg) |
49 | len = tp->t_maxseg; | |
4aed14e3 BJ |
50 | if (len < 0) |
51 | len = 0; /* FIN can cause -1 */ | |
0974b45c | 52 | flags = tcp_outflags[tp->t_state]; |
405c9168 BJ |
53 | if (len < so->so_snd.sb_cc) |
54 | flags &= ~TH_FIN; | |
0974b45c | 55 | if (len || (flags & (TH_SYN|TH_RST))) |
a6503abf BJ |
56 | goto send; |
57 | ||
58 | /* | |
0974b45c | 59 | * See if we owe peer an ACK or have a unacked FIN to send. |
a6503abf | 60 | */ |
0974b45c | 61 | if (tp->t_flags & TF_ACKNOW) |
a6503abf | 62 | goto send; |
0974b45c BJ |
63 | if ((so->so_state & SS_CANTSENDMORE) && |
64 | TCPS_OURFINNOTACKED(tp->t_state)) | |
a6503abf | 65 | goto send; |
76ee76df | 66 | |
a6503abf BJ |
67 | /* |
68 | * Calculate available window in i, and also amount | |
69 | * of window known to peer (as advertised window less | |
70 | * next expected input.) If this is 35% or more of the | |
71 | * maximum possible window, then want to send a segment to peer. | |
72 | */ | |
0974b45c BJ |
73 | win = sbspace(&so->so_rcv); |
74 | if (win > 0 && | |
75 | ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35)) | |
a6503abf BJ |
76 | goto send; |
77 | ||
78 | /* | |
79 | * No reason to send a segment, just return. | |
80 | */ | |
4aed14e3 | 81 | printf("tcp_output: nothing to send\n"); |
f1b2fa5b | 82 | return (0); |
a6503abf BJ |
83 | |
84 | send: | |
85 | /* | |
86 | * Grab a header mbuf, attaching a copy of data to | |
87 | * be transmitted, and initialize the header from | |
88 | * the template for sends on this connection. | |
89 | */ | |
76ee76df BJ |
90 | MGET(m, 0); |
91 | if (m == 0) | |
92 | return (0); | |
4aed14e3 | 93 | m->m_off = MMAXOFF - sizeof (struct tcpiphdr); |
53a5409e | 94 | m->m_len = sizeof (struct tcpiphdr); |
a6503abf BJ |
95 | if (len) { |
96 | m->m_next = m_copy(so->so_snd.sb_mb, off, len); | |
97 | if (m->m_next == 0) | |
98 | len = 0; | |
4aed14e3 | 99 | if (m->m_next) printf("copy *mtod()=%x\n", *mtod(m->m_next, char *)); |
a6503abf BJ |
100 | } |
101 | ti = mtod(m, struct tcpiphdr *); | |
102 | if (tp->t_template == 0) | |
103 | panic("tcp_output"); | |
f1b2fa5b | 104 | bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); |
a6503abf BJ |
105 | |
106 | /* | |
107 | * Fill in fields, remembering maximum advertised | |
108 | * window for use in delaying messages about window sizes. | |
109 | */ | |
4aed14e3 BJ |
110 | ti->ti_seq = tp->snd_nxt; |
111 | ti->ti_ack = tp->rcv_nxt; | |
112 | #if vax | |
113 | ti->ti_seq = htonl(ti->ti_seq); | |
114 | ti->ti_ack = htonl(ti->ti_ack); | |
115 | #endif | |
0974b45c | 116 | if (tp->t_tcpopt) { |
f1b2fa5b | 117 | m0 = m->m_next; |
0974b45c BJ |
118 | m->m_next = m_get(0); |
119 | if (m->m_next == 0) { | |
120 | (void) m_free(m); | |
f1b2fa5b | 121 | m_freem(m); |
0974b45c BJ |
122 | return (0); |
123 | } | |
124 | m->m_next->m_next = m0; | |
125 | m->m_off = MMINOFF; | |
126 | m->m_len = tp->t_tcpopt->m_len; | |
127 | bcopy(mtod(tp->t_tcpopt, caddr_t), mtod(m, caddr_t), | |
f1b2fa5b | 128 | (unsigned)tp->t_tcpopt->m_len); |
0974b45c BJ |
129 | ti->ti_off = (sizeof (struct tcphdr)+tp->t_tcpopt->m_len) >> 2; |
130 | } | |
131 | ti->ti_flags = flags; | |
a6503abf BJ |
132 | win = sbspace(&so->so_rcv); |
133 | if (win > 0) | |
f1b2fa5b | 134 | ti->ti_win = htons((u_short)win); |
0974b45c BJ |
135 | if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { |
136 | ti->ti_urp = htons((u_short)(tp->snd_up - tp->snd_nxt)); | |
a6503abf BJ |
137 | ti->ti_flags |= TH_URG; |
138 | } else | |
139 | /* | |
140 | * If no urgent pointer to send, then we pull | |
141 | * the urgent pointer to the left edge of the send window | |
142 | * so that it doesn't drift into the send window on sequence | |
143 | * number wraparound. | |
144 | */ | |
0974b45c BJ |
145 | tp->snd_up = tp->snd_una; /* drag it along */ |
146 | /* PUSH */ | |
a6503abf BJ |
147 | |
148 | /* | |
149 | * Put TCP length in extended header, and then | |
150 | * checksum extended header and data. | |
151 | */ | |
152 | if (len) | |
153 | ti->ti_len = htons((u_short)(len + sizeof (struct tcphdr))); | |
0974b45c BJ |
154 | ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + len); |
155 | ||
4aed14e3 BJ |
156 | printf("tcp_output: ti %x flags %x seq %x ack %x win %d len %d sum %x\n", |
157 | ti, ti->ti_flags, htonl(ti->ti_seq), htonl(ti->ti_ack), htons(ti->ti_win), ti->ti_len, ti->ti_sum); | |
158 | ||
0974b45c BJ |
159 | /* |
160 | * Advance snd_nxt over sequence space of this segment | |
161 | */ | |
162 | if (flags & (TH_SYN|TH_FIN)) | |
4aed14e3 | 163 | tp->snd_nxt++; |
0974b45c BJ |
164 | tp->snd_nxt += len; |
165 | ||
166 | /* | |
405c9168 | 167 | * If this transmission closes the window, |
4aed14e3 BJ |
168 | * start persistance timer at 2 round trip times |
169 | * but at least TCPTV_PERSMIN ticks. | |
0974b45c | 170 | */ |
4aed14e3 BJ |
171 | if (SEQ_GT(tp->snd_nxt, tp->snd_una+tp->snd_wnd) && |
172 | tp->t_timer[TCPT_PERSIST] == 0) | |
173 | TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], | |
174 | 2 * tp->t_srtt, TCPTV_PERSMIN, TCPTV_MAX); | |
405c9168 BJ |
175 | |
176 | /* | |
177 | * Time this transmission if not a retransmission and | |
178 | * not currently timing anything. | |
179 | */ | |
180 | if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) { | |
181 | tp->t_rtt = 1; | |
182 | tp->t_rtseq = tp->snd_nxt - len; | |
183 | } | |
184 | ||
185 | /* | |
186 | * Set retransmit timer if not currently set. | |
4aed14e3 | 187 | * Initial value for retransmit timer to tcp_beta*tp->t_srtt. |
405c9168 BJ |
188 | * Initialize shift counter which is used for exponential |
189 | * backoff of retransmit time. | |
190 | */ | |
4aed14e3 BJ |
191 | if (tp->t_timer[TCPT_REXMT] == 0 && tp->snd_nxt != tp->snd_una) { |
192 | TCPT_RANGESET(tp->t_timer[TCPT_REXMT], | |
193 | tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); | |
194 | printf("rexmt timer set to %d\n", tp->t_timer[TCPT_REXMT]); | |
405c9168 | 195 | tp->t_rxtshift = 0; |
0974b45c | 196 | } |
4aed14e3 | 197 | else printf("REXMT timer is already %d, snd_nxt %x snd_una %x\n", tp->t_timer[TCPT_REXMT], tp->snd_nxt, tp->snd_una); |
a6503abf BJ |
198 | |
199 | /* | |
200 | * Fill in IP length and desired time to live and | |
201 | * send to IP level. | |
202 | */ | |
203 | ((struct ip *)ti)->ip_len = len + sizeof (struct tcpiphdr); | |
204 | ((struct ip *)ti)->ip_ttl = TCP_TTL; | |
4aed14e3 BJ |
205 | if (ip_output(m, tp->t_ipopt) == 0) { |
206 | printf("ip_output failed\n"); | |
0974b45c | 207 | return (0); |
4aed14e3 | 208 | } |
a6503abf BJ |
209 | |
210 | /* | |
211 | * Data sent (as far as we can tell). | |
212 | * If this advertises a larger window than any other segment, | |
4aed14e3 | 213 | * then remember the size of the advertised window. |
0974b45c | 214 | * Drop send for purpose of ACK requirements. |
a6503abf | 215 | */ |
4aed14e3 | 216 | if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) { |
a6503abf | 217 | tp->rcv_adv = tp->rcv_nxt + win; |
4aed14e3 | 218 | } |
0974b45c | 219 | tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); |
4aed14e3 BJ |
220 | if (SEQ_GT(tp->snd_nxt, tp->snd_max)) |
221 | tp->snd_max = tp->snd_nxt; | |
0974b45c | 222 | return (1); |
76ee76df | 223 | } |