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29 * @(#)tcp.h 8.1 (Berkeley) 6/10/93
33 #ifndef _NETINET_TCP_H_
34 #define _NETINET_TCP_H_
36 #include <sys/cdefs.h>
40 typedef u_int32_t tcp_seq;
42 #define tcp6_seq tcp_seq /* for KAME src sync over BSD*'s */
43 #define tcp6hdr tcphdr /* for KAME src sync over BSD*'s */
47 * Per RFC 793, September, 1981.
50 u_short th_sport; /* source port */
51 u_short th_dport; /* destination port */
52 tcp_seq th_seq; /* sequence number */
53 tcp_seq th_ack; /* acknowledgement number */
54 #if BYTE_ORDER == LITTLE_ENDIAN
55 u_char th_x2:4, /* (unused) */
56 th_off:4; /* data offset */
58 #if BYTE_ORDER == BIG_ENDIAN
59 u_char th_off:4, /* data offset */
60 th_x2:4; /* (unused) */
71 #define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG|TH_ECE|TH_CWR)
72 #define PRINT_TH_FLAGS "\20\1FIN\2SYN\3RST\4PUSH\5ACK\6URG\7ECE\10CWR"
74 u_short th_win; /* window */
75 u_short th_sum; /* checksum */
76 u_short th_urp; /* urgent pointer */
81 #define TCPOPT_PAD 0 /* padding after EOL */
85 #define TCPOPT_MAXSEG 2
86 #define TCPOLEN_MAXSEG 4
87 #define TCPOPT_WINDOW 3
88 #define TCPOLEN_WINDOW 3
89 #define TCPOPT_SACK_PERMITTED 4
90 #define TCPOLEN_SACK_PERMITTED 2
92 #define TCPOLEN_SACKHDR 2
93 #define TCPOLEN_SACK 8 /* 2*sizeof(tcp_seq) */
94 #define TCPOPT_TIMESTAMP 8
95 #define TCPOLEN_TIMESTAMP 10
96 #define TCPOLEN_TSTAMP_APPA (TCPOLEN_TIMESTAMP+2) /* appendix A */
97 #define TCPOPT_SIGNATURE 19 /* Keyed MD5: RFC 2385 */
98 #define TCPOLEN_SIGNATURE 18
100 /* Miscellaneous constants */
101 #define MAX_SACK_BLKS 6 /* Max # SACK blocks stored at receiver side */
102 #define TCP_MAX_SACK 4 /* MAX # SACKs sent in any segment */
106 * The default maximum segment size (MSS) to be used for new TCP connections
107 * when path MTU discovery is not enabled.
109 * RFC879 derives the default MSS from the largest datagram size hosts are
110 * minimally required to handle directly or through IP reassembly minus the
111 * size of the IP and TCP header. With IPv6 the minimum MTU is specified
114 * For IPv4 the MSS is 576 - sizeof(struct tcpiphdr)
115 * For IPv6 the MSS is IPV6_MMTU - sizeof(struct ip6_hdr) - sizeof(struct tcphdr)
117 * We use explicit numerical definition here to avoid header pollution.
120 #define TCP6_MSS 1220
123 * Limit the lowest MSS we accept for path MTU discovery and the TCP SYN MSS
124 * option. Allowing low values of MSS can consume significant resources and
125 * be used to mount a resource exhaustion attack.
126 * Connections requesting lower MSS values will be rounded up to this value
127 * and the IP_DF flag will be cleared to allow fragmentation along the path.
129 * See tcp_subr.c tcp_minmss SYSCTL declaration for more comments. Setting
130 * it to "0" disables the minmss check.
132 * The default value is fine for TCP across the Internet's smallest official
133 * link MTU (256 bytes for AX.25 packet radio). However, a connection is very
134 * unlikely to come across such low MTU interfaces these days (anno domini 2003).
136 #define TCP_MINMSS 216
138 #define TCP_MAXWIN 65535 /* largest value for (unscaled) window */
139 #define TTCP_CLIENT_SND_WND 4096 /* dflt send window for T/TCP client */
141 #define TCP_MAX_WINSHIFT 14 /* maximum window shift */
143 #define TCP_MAXBURST 4 /* maximum segments in a burst */
145 #define TCP_MAXHLEN (0xf<<2) /* max length of header in bytes */
146 #define TCP_MAXOLEN (TCP_MAXHLEN - sizeof(struct tcphdr))
147 /* max space left for options */
148 #endif /* __BSD_VISIBLE */
151 * User-settable options (used with setsockopt).
153 #define TCP_NODELAY 0x01 /* don't delay send to coalesce packets */
155 #define TCP_MAXSEG 0x02 /* set maximum segment size */
156 #define TCP_NOPUSH 0x04 /* don't push last block of write */
157 #define TCP_NOOPT 0x08 /* don't use TCP options */
158 #define TCP_MD5SIG 0x10 /* use MD5 digests (RFC2385) */
159 #define TCP_INFO 0x20 /* retrieve tcp_info structure */
160 #define TCP_CONGESTION 0x40 /* get/set congestion control algorithm */
162 #define TCP_CA_NAME_MAX 16 /* max congestion control name length */
164 #define TCPI_OPT_TIMESTAMPS 0x01
165 #define TCPI_OPT_SACK 0x02
166 #define TCPI_OPT_WSCALE 0x04
167 #define TCPI_OPT_ECN 0x08
168 #define TCPI_OPT_TOE 0x10
171 * The TCP_INFO socket option comes from the Linux 2.6 TCP API, and permits
172 * the caller to query certain information about the state of a TCP
173 * connection. We provide an overlapping set of fields with the Linux
174 * implementation, but since this is a fixed size structure, room has been
175 * left for growth. In order to maximize potential future compatibility with
176 * the Linux API, the same variable names and order have been adopted, and
177 * padding left to make room for omitted fields in case they are added later.
179 * XXX: This is currently an unstable ABI/API, in that it is expected to
183 u_int8_t tcpi_state; /* TCP FSM state. */
184 u_int8_t __tcpi_ca_state;
185 u_int8_t __tcpi_retransmits;
186 u_int8_t __tcpi_probes;
187 u_int8_t __tcpi_backoff;
188 u_int8_t tcpi_options; /* Options enabled on conn. */
189 u_int8_t tcpi_snd_wscale:4, /* RFC1323 send shift value. */
190 tcpi_rcv_wscale:4; /* RFC1323 recv shift value. */
192 u_int32_t tcpi_rto; /* Retransmission timeout (usec). */
193 u_int32_t __tcpi_ato;
194 u_int32_t tcpi_snd_mss; /* Max segment size for send. */
195 u_int32_t tcpi_rcv_mss; /* Max segment size for receive. */
197 u_int32_t __tcpi_unacked;
198 u_int32_t __tcpi_sacked;
199 u_int32_t __tcpi_lost;
200 u_int32_t __tcpi_retrans;
201 u_int32_t __tcpi_fackets;
203 /* Times; measurements in usecs. */
204 u_int32_t __tcpi_last_data_sent;
205 u_int32_t __tcpi_last_ack_sent; /* Also unimpl. on Linux? */
206 u_int32_t tcpi_last_data_recv; /* Time since last recv data. */
207 u_int32_t __tcpi_last_ack_recv;
209 /* Metrics; variable units. */
210 u_int32_t __tcpi_pmtu;
211 u_int32_t __tcpi_rcv_ssthresh;
212 u_int32_t tcpi_rtt; /* Smoothed RTT in usecs. */
213 u_int32_t tcpi_rttvar; /* RTT variance in usecs. */
214 u_int32_t tcpi_snd_ssthresh; /* Slow start threshold. */
215 u_int32_t tcpi_snd_cwnd; /* Send congestion window. */
216 u_int32_t __tcpi_advmss;
217 u_int32_t __tcpi_reordering;
219 u_int32_t __tcpi_rcv_rtt;
220 u_int32_t tcpi_rcv_space; /* Advertised recv window. */
222 /* FreeBSD extensions to tcp_info. */
223 u_int32_t tcpi_snd_wnd; /* Advertised send window. */
224 u_int32_t tcpi_snd_bwnd; /* No longer used. */
225 u_int32_t tcpi_snd_nxt; /* Next egress seqno */
226 u_int32_t tcpi_rcv_nxt; /* Next ingress seqno */
227 u_int32_t tcpi_toe_tid; /* HWTID for TOE endpoints */
228 u_int32_t tcpi_snd_rexmitpack; /* Retransmitted packets */
229 u_int32_t tcpi_rcv_ooopack; /* Out-of-order packets */
230 u_int32_t tcpi_snd_zerowin; /* Zero-sized windows sent */
232 /* Padding to grow without breaking ABI. */
233 u_int32_t __tcpi_pad[26]; /* Padding. */
237 #endif /* !_NETINET_TCP_H_ */