1 /* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */ 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * Definitions for the TCP protocol. 8 * 9 * Version: @(#)tcp.h 1.0.2 04/28/93 10 * 11 * Author: Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 12 * 13 * This program is free software; you can redistribute it and/or 14 * modify it under the terms of the GNU General Public License 15 * as published by the Free Software Foundation; either version 16 * 2 of the License, or (at your option) any later version. 17 */ 18 #ifndef _UAPI_LINUX_TCP_H 19 #define _UAPI_LINUX_TCP_H 20 21 #include <linux/types.h> 22 #include <asm/byteorder.h> 23 #include <linux/socket.h> 24 25 struct tcphdr { 26 __be16 source; 27 __be16 dest; 28 __be32 seq; 29 __be32 ack_seq; 30 #if defined(__LITTLE_ENDIAN_BITFIELD) 31 __u16 ae:1, 32 res1:3, 33 doff:4, 34 fin:1, 35 syn:1, 36 rst:1, 37 psh:1, 38 ack:1, 39 urg:1, 40 ece:1, 41 cwr:1; 42 #elif defined(__BIG_ENDIAN_BITFIELD) 43 __u16 doff:4, 44 res1:3, 45 ae:1, 46 cwr:1, 47 ece:1, 48 urg:1, 49 ack:1, 50 psh:1, 51 rst:1, 52 syn:1, 53 fin:1; 54 #else 55 #error "Adjust your <asm/byteorder.h> defines" 56 #endif 57 __be16 window; 58 __sum16 check; 59 __be16 urg_ptr; 60 }; 61 62 /* 63 * The union cast uses a gcc extension to avoid aliasing problems 64 * (union is compatible to any of its members) 65 * This means this part of the code is -fstrict-aliasing safe now. 66 */ 67 union tcp_word_hdr { 68 struct tcphdr hdr; 69 __be32 words[5]; 70 }; 71 72 #define tcp_flag_word(tp) (((union tcp_word_hdr *)(tp))->words[3]) 73 74 enum { 75 TCP_FLAG_AE = __constant_cpu_to_be32(0x01000000), 76 TCP_FLAG_CWR = __constant_cpu_to_be32(0x00800000), 77 TCP_FLAG_ECE = __constant_cpu_to_be32(0x00400000), 78 TCP_FLAG_URG = __constant_cpu_to_be32(0x00200000), 79 TCP_FLAG_ACK = __constant_cpu_to_be32(0x00100000), 80 TCP_FLAG_PSH = __constant_cpu_to_be32(0x00080000), 81 TCP_FLAG_RST = __constant_cpu_to_be32(0x00040000), 82 TCP_FLAG_SYN = __constant_cpu_to_be32(0x00020000), 83 TCP_FLAG_FIN = __constant_cpu_to_be32(0x00010000), 84 TCP_RESERVED_BITS = __constant_cpu_to_be32(0x0E000000), 85 TCP_DATA_OFFSET = __constant_cpu_to_be32(0xF0000000) 86 }; 87 88 /* 89 * TCP general constants 90 */ 91 #define TCP_MSS_DEFAULT 536U /* IPv4 (RFC1122, RFC2581) */ 92 #define TCP_MSS_DESIRED 1220U /* IPv6 (tunneled), EDNS0 (RFC3226) */ 93 94 /* TCP socket options */ 95 #define TCP_NODELAY 1 /* Turn off Nagle's algorithm. */ 96 #define TCP_MAXSEG 2 /* Limit MSS */ 97 #define TCP_CORK 3 /* Never send partially complete segments */ 98 #define TCP_KEEPIDLE 4 /* Start keeplives after this period */ 99 #define TCP_KEEPINTVL 5 /* Interval between keepalives */ 100 #define TCP_KEEPCNT 6 /* Number of keepalives before death */ 101 #define TCP_SYNCNT 7 /* Number of SYN retransmits */ 102 #define TCP_LINGER2 8 /* Life time of orphaned FIN-WAIT-2 state */ 103 #define TCP_DEFER_ACCEPT 9 /* Wake up listener only when data arrive */ 104 #define TCP_WINDOW_CLAMP 10 /* Bound advertised window */ 105 #define TCP_INFO 11 /* Information about this connection. */ 106 #define TCP_QUICKACK 12 /* Block/reenable quick acks */ 107 #define TCP_CONGESTION 13 /* Congestion control algorithm */ 108 #define TCP_MD5SIG 14 /* TCP MD5 Signature (RFC2385) */ 109 #define TCP_THIN_LINEAR_TIMEOUTS 16 /* Use linear timeouts for thin streams*/ 110 #define TCP_THIN_DUPACK 17 /* Fast retrans. after 1 dupack */ 111 #define TCP_USER_TIMEOUT 18 /* How long for loss retry before timeout */ 112 #define TCP_REPAIR 19 /* TCP sock is under repair right now */ 113 #define TCP_REPAIR_QUEUE 20 114 #define TCP_QUEUE_SEQ 21 115 #define TCP_REPAIR_OPTIONS 22 116 #define TCP_FASTOPEN 23 /* Enable FastOpen on listeners */ 117 #define TCP_TIMESTAMP 24 118 #define TCP_NOTSENT_LOWAT 25 /* limit number of unsent bytes in write queue */ 119 #define TCP_CC_INFO 26 /* Get Congestion Control (optional) info */ 120 #define TCP_SAVE_SYN 27 /* Record SYN headers for new connections */ 121 #define TCP_SAVED_SYN 28 /* Get SYN headers recorded for connection */ 122 #define TCP_REPAIR_WINDOW 29 /* Get/set window parameters */ 123 #define TCP_FASTOPEN_CONNECT 30 /* Attempt FastOpen with connect */ 124 #define TCP_ULP 31 /* Attach a ULP to a TCP connection */ 125 #define TCP_MD5SIG_EXT 32 /* TCP MD5 Signature with extensions */ 126 #define TCP_FASTOPEN_KEY 33 /* Set the key for Fast Open (cookie) */ 127 #define TCP_FASTOPEN_NO_COOKIE 34 /* Enable TFO without a TFO cookie */ 128 #define TCP_ZEROCOPY_RECEIVE 35 129 #define TCP_INQ 36 /* Notify bytes available to read as a cmsg on read */ 130 131 #define TCP_CM_INQ TCP_INQ 132 133 #define TCP_TX_DELAY 37 /* delay outgoing packets by XX usec */ 134 135 #define TCP_AO_ADD_KEY 38 /* Add/Set MKT */ 136 #define TCP_AO_DEL_KEY 39 /* Delete MKT */ 137 #define TCP_AO_INFO 40 /* Set/list TCP-AO per-socket options */ 138 #define TCP_AO_GET_KEYS 41 /* List MKT(s) */ 139 #define TCP_AO_REPAIR 42 /* Get/Set SNEs and ISNs */ 140 141 #define TCP_IS_MPTCP 43 /* Is MPTCP being used? */ 142 #define TCP_RTO_MAX_MS 44 /* max rto time in ms */ 143 #define TCP_RTO_MIN_US 45 /* min rto time in us */ 144 #define TCP_DELACK_MAX_US 46 /* max delayed ack time in us */ 145 146 #define TCP_REPAIR_ON 1 147 #define TCP_REPAIR_OFF 0 148 #define TCP_REPAIR_OFF_NO_WP -1 /* Turn off without window probes */ 149 150 struct tcp_repair_opt { 151 __u32 opt_code; 152 __u32 opt_val; 153 }; 154 155 struct tcp_repair_window { 156 __u32 snd_wl1; 157 __u32 snd_wnd; 158 __u32 max_window; 159 160 __u32 rcv_wnd; 161 __u32 rcv_wup; 162 }; 163 164 enum { 165 TCP_NO_QUEUE, 166 TCP_RECV_QUEUE, 167 TCP_SEND_QUEUE, 168 TCP_QUEUES_NR, 169 }; 170 171 /* why fastopen failed from client perspective */ 172 enum tcp_fastopen_client_fail { 173 TFO_STATUS_UNSPEC, /* catch-all */ 174 TFO_COOKIE_UNAVAILABLE, /* if not in TFO_CLIENT_NO_COOKIE mode */ 175 TFO_DATA_NOT_ACKED, /* SYN-ACK did not ack SYN data */ 176 TFO_SYN_RETRANSMITTED, /* SYN-ACK did not ack SYN data after timeout */ 177 }; 178 179 /* for TCP_INFO socket option */ 180 #define TCPI_OPT_TIMESTAMPS 1 181 #define TCPI_OPT_SACK 2 182 #define TCPI_OPT_WSCALE 4 183 #define TCPI_OPT_ECN 8 /* ECN was negociated at TCP session init */ 184 #define TCPI_OPT_ECN_SEEN 16 /* we received at least one packet with ECT */ 185 #define TCPI_OPT_SYN_DATA 32 /* SYN-ACK acked data in SYN sent or rcvd */ 186 #define TCPI_OPT_USEC_TS 64 /* usec timestamps */ 187 188 /* 189 * Sender's congestion state indicating normal or abnormal situations 190 * in the last round of packets sent. The state is driven by the ACK 191 * information and timer events. 192 */ 193 enum tcp_ca_state { 194 /* 195 * Nothing bad has been observed recently. 196 * No apparent reordering, packet loss, or ECN marks. 197 */ 198 TCP_CA_Open = 0, 199 #define TCPF_CA_Open (1<<TCP_CA_Open) 200 /* 201 * The sender enters disordered state when it has received DUPACKs or 202 * SACKs in the last round of packets sent. This could be due to packet 203 * loss or reordering but needs further information to confirm packets 204 * have been lost. 205 */ 206 TCP_CA_Disorder = 1, 207 #define TCPF_CA_Disorder (1<<TCP_CA_Disorder) 208 /* 209 * The sender enters Congestion Window Reduction (CWR) state when it 210 * has received ACKs with ECN-ECE marks, or has experienced congestion 211 * or packet discard on the sender host (e.g. qdisc). 212 */ 213 TCP_CA_CWR = 2, 214 #define TCPF_CA_CWR (1<<TCP_CA_CWR) 215 /* 216 * The sender is in fast recovery and retransmitting lost packets, 217 * typically triggered by ACK events. 218 */ 219 TCP_CA_Recovery = 3, 220 #define TCPF_CA_Recovery (1<<TCP_CA_Recovery) 221 /* 222 * The sender is in loss recovery triggered by retransmission timeout. 223 */ 224 TCP_CA_Loss = 4 225 #define TCPF_CA_Loss (1<<TCP_CA_Loss) 226 }; 227 228 struct tcp_info { 229 __u8 tcpi_state; 230 __u8 tcpi_ca_state; 231 __u8 tcpi_retransmits; 232 __u8 tcpi_probes; 233 __u8 tcpi_backoff; 234 __u8 tcpi_options; 235 __u8 tcpi_snd_wscale : 4, tcpi_rcv_wscale : 4; 236 __u8 tcpi_delivery_rate_app_limited:1, tcpi_fastopen_client_fail:2; 237 238 __u32 tcpi_rto; 239 __u32 tcpi_ato; 240 __u32 tcpi_snd_mss; 241 __u32 tcpi_rcv_mss; 242 243 __u32 tcpi_unacked; 244 __u32 tcpi_sacked; 245 __u32 tcpi_lost; 246 __u32 tcpi_retrans; 247 __u32 tcpi_fackets; 248 249 /* Times. */ 250 __u32 tcpi_last_data_sent; 251 __u32 tcpi_last_ack_sent; /* Not remembered, sorry. */ 252 __u32 tcpi_last_data_recv; 253 __u32 tcpi_last_ack_recv; 254 255 /* Metrics. */ 256 __u32 tcpi_pmtu; 257 __u32 tcpi_rcv_ssthresh; 258 __u32 tcpi_rtt; 259 __u32 tcpi_rttvar; 260 __u32 tcpi_snd_ssthresh; 261 __u32 tcpi_snd_cwnd; 262 __u32 tcpi_advmss; 263 __u32 tcpi_reordering; 264 265 __u32 tcpi_rcv_rtt; 266 __u32 tcpi_rcv_space; 267 268 __u32 tcpi_total_retrans; 269 270 __u64 tcpi_pacing_rate; 271 __u64 tcpi_max_pacing_rate; 272 __u64 tcpi_bytes_acked; /* RFC4898 tcpEStatsAppHCThruOctetsAcked */ 273 __u64 tcpi_bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived */ 274 __u32 tcpi_segs_out; /* RFC4898 tcpEStatsPerfSegsOut */ 275 __u32 tcpi_segs_in; /* RFC4898 tcpEStatsPerfSegsIn */ 276 277 __u32 tcpi_notsent_bytes; 278 __u32 tcpi_min_rtt; 279 __u32 tcpi_data_segs_in; /* RFC4898 tcpEStatsDataSegsIn */ 280 __u32 tcpi_data_segs_out; /* RFC4898 tcpEStatsDataSegsOut */ 281 282 __u64 tcpi_delivery_rate; 283 284 __u64 tcpi_busy_time; /* Time (usec) busy sending data */ 285 __u64 tcpi_rwnd_limited; /* Time (usec) limited by receive window */ 286 __u64 tcpi_sndbuf_limited; /* Time (usec) limited by send buffer */ 287 288 __u32 tcpi_delivered; 289 __u32 tcpi_delivered_ce; 290 291 __u64 tcpi_bytes_sent; /* RFC4898 tcpEStatsPerfHCDataOctetsOut */ 292 __u64 tcpi_bytes_retrans; /* RFC4898 tcpEStatsPerfOctetsRetrans */ 293 __u32 tcpi_dsack_dups; /* RFC4898 tcpEStatsStackDSACKDups */ 294 __u32 tcpi_reord_seen; /* reordering events seen */ 295 296 __u32 tcpi_rcv_ooopack; /* Out-of-order packets received */ 297 298 __u32 tcpi_snd_wnd; /* peer's advertised receive window after 299 * scaling (bytes) 300 */ 301 __u32 tcpi_rcv_wnd; /* local advertised receive window after 302 * scaling (bytes) 303 */ 304 305 __u32 tcpi_rehash; /* PLB or timeout triggered rehash attempts */ 306 307 __u16 tcpi_total_rto; /* Total number of RTO timeouts, including 308 * SYN/SYN-ACK and recurring timeouts. 309 */ 310 __u16 tcpi_total_rto_recoveries; /* Total number of RTO 311 * recoveries, including any 312 * unfinished recovery. 313 */ 314 __u32 tcpi_total_rto_time; /* Total time spent in RTO recoveries 315 * in milliseconds, including any 316 * unfinished recovery. 317 */ 318 }; 319 320 /* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */ 321 enum { 322 TCP_NLA_PAD, 323 TCP_NLA_BUSY, /* Time (usec) busy sending data */ 324 TCP_NLA_RWND_LIMITED, /* Time (usec) limited by receive window */ 325 TCP_NLA_SNDBUF_LIMITED, /* Time (usec) limited by send buffer */ 326 TCP_NLA_DATA_SEGS_OUT, /* Data pkts sent including retransmission */ 327 TCP_NLA_TOTAL_RETRANS, /* Data pkts retransmitted */ 328 TCP_NLA_PACING_RATE, /* Pacing rate in bytes per second */ 329 TCP_NLA_DELIVERY_RATE, /* Delivery rate in bytes per second */ 330 TCP_NLA_SND_CWND, /* Sending congestion window */ 331 TCP_NLA_REORDERING, /* Reordering metric */ 332 TCP_NLA_MIN_RTT, /* minimum RTT */ 333 TCP_NLA_RECUR_RETRANS, /* Recurring retransmits for the current pkt */ 334 TCP_NLA_DELIVERY_RATE_APP_LMT, /* delivery rate application limited ? */ 335 TCP_NLA_SNDQ_SIZE, /* Data (bytes) pending in send queue */ 336 TCP_NLA_CA_STATE, /* ca_state of socket */ 337 TCP_NLA_SND_SSTHRESH, /* Slow start size threshold */ 338 TCP_NLA_DELIVERED, /* Data pkts delivered incl. out-of-order */ 339 TCP_NLA_DELIVERED_CE, /* Like above but only ones w/ CE marks */ 340 TCP_NLA_BYTES_SENT, /* Data bytes sent including retransmission */ 341 TCP_NLA_BYTES_RETRANS, /* Data bytes retransmitted */ 342 TCP_NLA_DSACK_DUPS, /* DSACK blocks received */ 343 TCP_NLA_REORD_SEEN, /* reordering events seen */ 344 TCP_NLA_SRTT, /* smoothed RTT in usecs */ 345 TCP_NLA_TIMEOUT_REHASH, /* Timeout-triggered rehash attempts */ 346 TCP_NLA_BYTES_NOTSENT, /* Bytes in write queue not yet sent */ 347 TCP_NLA_EDT, /* Earliest departure time (CLOCK_MONOTONIC) */ 348 TCP_NLA_TTL, /* TTL or hop limit of a packet received */ 349 TCP_NLA_REHASH, /* PLB and timeout triggered rehash attempts */ 350 }; 351 352 /* for TCP_MD5SIG socket option */ 353 #define TCP_MD5SIG_MAXKEYLEN 80 354 355 /* tcp_md5sig extension flags for TCP_MD5SIG_EXT */ 356 #define TCP_MD5SIG_FLAG_PREFIX 0x1 /* address prefix length */ 357 #define TCP_MD5SIG_FLAG_IFINDEX 0x2 /* ifindex set */ 358 359 struct tcp_md5sig { 360 struct __kernel_sockaddr_storage tcpm_addr; /* address associated */ 361 __u8 tcpm_flags; /* extension flags */ 362 __u8 tcpm_prefixlen; /* address prefix */ 363 __u16 tcpm_keylen; /* key length */ 364 int tcpm_ifindex; /* device index for scope */ 365 __u8 tcpm_key[TCP_MD5SIG_MAXKEYLEN]; /* key (binary) */ 366 }; 367 368 /* INET_DIAG_MD5SIG */ 369 struct tcp_diag_md5sig { 370 __u8 tcpm_family; 371 __u8 tcpm_prefixlen; 372 __u16 tcpm_keylen; 373 __be32 tcpm_addr[4]; 374 __u8 tcpm_key[TCP_MD5SIG_MAXKEYLEN]; 375 }; 376 377 #define TCP_AO_MAXKEYLEN 80 378 379 #define TCP_AO_KEYF_IFINDEX (1 << 0) /* L3 ifindex for VRF */ 380 #define TCP_AO_KEYF_EXCLUDE_OPT (1 << 1) /* "Indicates whether TCP 381 * options other than TCP-AO 382 * are included in the MAC 383 * calculation" 384 */ 385 386 struct tcp_ao_add { /* setsockopt(TCP_AO_ADD_KEY) */ 387 struct __kernel_sockaddr_storage addr; /* peer's address for the key */ 388 char alg_name[64]; /* crypto hash algorithm to use */ 389 __s32 ifindex; /* L3 dev index for VRF */ 390 __u32 set_current :1, /* set key as Current_key at once */ 391 set_rnext :1, /* request it from peer with RNext_key */ 392 reserved :30; /* must be 0 */ 393 __u16 reserved2; /* padding, must be 0 */ 394 __u8 prefix; /* peer's address prefix */ 395 __u8 sndid; /* SendID for outgoing segments */ 396 __u8 rcvid; /* RecvID to match for incoming seg */ 397 __u8 maclen; /* length of authentication code (hash) */ 398 __u8 keyflags; /* see TCP_AO_KEYF_ */ 399 __u8 keylen; /* length of ::key */ 400 __u8 key[TCP_AO_MAXKEYLEN]; 401 } __attribute__((aligned(8))); 402 403 struct tcp_ao_del { /* setsockopt(TCP_AO_DEL_KEY) */ 404 struct __kernel_sockaddr_storage addr; /* peer's address for the key */ 405 __s32 ifindex; /* L3 dev index for VRF */ 406 __u32 set_current :1, /* corresponding ::current_key */ 407 set_rnext :1, /* corresponding ::rnext */ 408 del_async :1, /* only valid for listen sockets */ 409 reserved :29; /* must be 0 */ 410 __u16 reserved2; /* padding, must be 0 */ 411 __u8 prefix; /* peer's address prefix */ 412 __u8 sndid; /* SendID for outgoing segments */ 413 __u8 rcvid; /* RecvID to match for incoming seg */ 414 __u8 current_key; /* KeyID to set as Current_key */ 415 __u8 rnext; /* KeyID to set as Rnext_key */ 416 __u8 keyflags; /* see TCP_AO_KEYF_ */ 417 } __attribute__((aligned(8))); 418 419 struct tcp_ao_info_opt { /* setsockopt(TCP_AO_INFO), getsockopt(TCP_AO_INFO) */ 420 /* Here 'in' is for setsockopt(), 'out' is for getsockopt() */ 421 __u32 set_current :1, /* in/out: corresponding ::current_key */ 422 set_rnext :1, /* in/out: corresponding ::rnext */ 423 ao_required :1, /* in/out: don't accept non-AO connects */ 424 set_counters :1, /* in: set/clear ::pkt_* counters */ 425 accept_icmps :1, /* in/out: accept incoming ICMPs */ 426 reserved :27; /* must be 0 */ 427 __u16 reserved2; /* padding, must be 0 */ 428 __u8 current_key; /* in/out: KeyID of Current_key */ 429 __u8 rnext; /* in/out: keyid of RNext_key */ 430 __u64 pkt_good; /* in/out: verified segments */ 431 __u64 pkt_bad; /* in/out: failed verification */ 432 __u64 pkt_key_not_found; /* in/out: could not find a key to verify */ 433 __u64 pkt_ao_required; /* in/out: segments missing TCP-AO sign */ 434 __u64 pkt_dropped_icmp; /* in/out: ICMPs that were ignored */ 435 } __attribute__((aligned(8))); 436 437 struct tcp_ao_getsockopt { /* getsockopt(TCP_AO_GET_KEYS) */ 438 struct __kernel_sockaddr_storage addr; /* in/out: dump keys for peer 439 * with this address/prefix 440 */ 441 char alg_name[64]; /* out: crypto hash algorithm */ 442 __u8 key[TCP_AO_MAXKEYLEN]; 443 __u32 nkeys; /* in: size of the userspace buffer 444 * @optval, measured in @optlen - the 445 * sizeof(struct tcp_ao_getsockopt) 446 * out: number of keys that matched 447 */ 448 __u16 is_current :1, /* in: match and dump Current_key, 449 * out: the dumped key is Current_key 450 */ 451 452 is_rnext :1, /* in: match and dump RNext_key, 453 * out: the dumped key is RNext_key 454 */ 455 get_all :1, /* in: dump all keys */ 456 reserved :13; /* padding, must be 0 */ 457 __u8 sndid; /* in/out: dump keys with SendID */ 458 __u8 rcvid; /* in/out: dump keys with RecvID */ 459 __u8 prefix; /* in/out: dump keys with address/prefix */ 460 __u8 maclen; /* out: key's length of authentication 461 * code (hash) 462 */ 463 __u8 keyflags; /* in/out: see TCP_AO_KEYF_ */ 464 __u8 keylen; /* out: length of ::key */ 465 __s32 ifindex; /* in/out: L3 dev index for VRF */ 466 __u64 pkt_good; /* out: verified segments */ 467 __u64 pkt_bad; /* out: segments that failed verification */ 468 } __attribute__((aligned(8))); 469 470 struct tcp_ao_repair { /* {s,g}etsockopt(TCP_AO_REPAIR) */ 471 __be32 snt_isn; 472 __be32 rcv_isn; 473 __u32 snd_sne; 474 __u32 rcv_sne; 475 } __attribute__((aligned(8))); 476 477 /* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */ 478 479 #define TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT 0x1 480 struct tcp_zerocopy_receive { 481 __u64 address; /* in: address of mapping */ 482 __u32 length; /* in/out: number of bytes to map/mapped */ 483 __u32 recv_skip_hint; /* out: amount of bytes to skip */ 484 __u32 inq; /* out: amount of bytes in read queue */ 485 __s32 err; /* out: socket error */ 486 __u64 copybuf_address; /* in: copybuf address (small reads) */ 487 __s32 copybuf_len; /* in/out: copybuf bytes avail/used or error */ 488 __u32 flags; /* in: flags */ 489 __u64 msg_control; /* ancillary data */ 490 __u64 msg_controllen; 491 __u32 msg_flags; 492 __u32 reserved; /* set to 0 for now */ 493 }; 494 #endif /* _UAPI_LINUX_TCP_H */ 495