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