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1 perry 1 IP
2 !!!IP
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 ADDRESS FORMAT
7 SOCKET OPTIONS
8 SYSCTLS
9 IOCTLS
10 NOTES
11 ERRORS
12 VERSIONS
13 COMPATIBILITY
14 BUGS
15 AUTHORS
16 SEE ALSO
17 ----
18 !!NAME
19
20
21 ip - Linux IPv4 protocol implementation
22 !!SYNOPSIS
23
24
25 __#include __
26 #include __
27
28
29 ''tcp_socket'' __= socket(PF_INET, SOCK_STREAM,
30 0);__''
31 raw_socket'' __= socket(PF_INET, SOCK_RAW,__
32 ''protocol''__);__''
33 udp_socket'' __= socket(PF_INET, SOCK_DGRAM,__
34 ''protocol''__);__
35 !!DESCRIPTION
36
37
38 Linux implements the Internet Protocol, version 4, described
39 in RFC791 and RFC1122. __ip__ contains a level 2
40 multicasting implementation conforming to RFC1112. It also
41 contains an IP router including a packet
42 filter.
43
44
45 The programmer's interface is BSD sockets compatible. For
46 more information on sockets, see
47 socket(7).
48
49
50 An IP socket is created by calling the socket(2)
51 function as __socket(PF_INET, socket_type, protocol)__.
52 Valid socket types are __SOCK_STREAM__ to open a
53 tcp(7) socket, __SOCK_DGRAM__ to open a
54 udp(7) socket, or __SOCK_RAW__ to open a
55 raw(7) socket to access the IP protocol directly.
56 ''protocol'' is the IP protocol in the IP header to be
57 received or sent. The only valid values for ''protocol''
58 are __0__ and __IPPROTO_TCP__ for TCP sockets and
59 __0__ and __IPPROTO_UDP__ for UDP sockets. For
60 __SOCK_RAW__ you may specify a valid IANA IP protocol
61 defined in RFC1700 assigned numbers.
62
63
64 When a process wants to receive new incoming packets or
65 connections, it should bind a socket to a local interface
66 address using bind(2). Only one IP socket may be
67 bound to any given local (address, port) pair. When
68 __INADDR_ANY__ is specified in the bind call the socket
69 will be bound to ''all'' local interfaces. When
70 listen(2) or connect(2) are called on a
71 unbound socket the socket is automatically bound to a random
72 free port with the local address set to
73 __INADDR_ANY__.
74
75
76 A TCP local socket address that has been bound is
77 unavailable for some time after closing, unless the
78 __SO_REUSEADDR__ flag has been set. Care should be taken
79 when using this flag as it makes TCP less
80 reliable.
81 !!ADDRESS FORMAT
82
83
84 An IP socket address is defined as a combination of an IP
85 interface address and a port number. The basic IP protocol
86 does not supply port numbers, they are implemented by higher
87 level protocols like udp(7) and tcp(7). On raw
88 sockets __sin_port__ is set to the IP
89 protocol.
90
91
5 ScottLamb 92 struct sockaddr_in {
93 sa_family_t sin_family; /* address family: AF_INET */
94 u_int16_t sin_port; /* port in network byte order */
95 struct in_addr sin_addr; /* internet address */
96 };
97 /* Internet address. */
98 struct in_addr {
99 u_int32_t s_addr; /* address in network byte order */
100 };
1 perry 101
102
103 ''sin_family'' is always set to __AF_INET__. This is
104 required; in Linux 2.2 most networking functions return
105 __EINVAL__ when this setting is missing. ''sin_port''
106 contains the port in network byte order. The port numbers
107 below 1024 are called ''reserved ports''. Only processes
108 with effective user id 0 or the __CAP_NET_BIND_SERVICE__
109 capability may bind(2) to these sockets. Note that
110 the raw IPv4 protocol as such has no concept of a port, they
111 are only implemented by higher protocols like tcp(7)
112 and udp(7).
113
114
115 ''sin_addr'' is the IP host address. The ''addr''
116 member of __struct in_addr__ contains the host interface
117 address in network order. __in_addr__ should be only
4 perry 118 accessed using the inet_aton(3), __inet_addr__(3),
119 inet_makeaddr(3) library functions or directly with
1 perry 120 the name resolver (see gethostbyname(3)). IPv4
121 addresses are divided into unicast, broadcast and multicast
122 addresses. Unicast addresses specify a single interface of a
123 host, broadcast addresses specify all hosts on a network and
124 multicast addresses address all hosts in a multicast group.
125 Datagrams to broadcast addresses can be only sent or
126 received when the __SO_BROADCAST__ socket flag is set. In
127 the current implementation connection oriented sockets are
128 only allowed to use unicast addresses.
129
130
131 Note that the address and the port are always stored in
132 network order. In particular, this means that you need to
133 call htons(3) on the number that is assigned to a
134 port. All address/port manipulation functions in the
135 standard library work in network order.
136
137
138 There are several special addresses: __INADDR_LOOPBACK__
139 (127.0.0.1) always refers to the local host via the loopback
140 device; __INADDR_ANY__ (0.0.0.0) means any address for
141 binding; __INADDR_BROADCAST__ (255.255.255.255) means any
142 host and has the same effect on bind as __INADDR_ANY__
143 for historical reasons.
144 !!SOCKET OPTIONS
145
146
147 IP supports some protocol specific socket options that can
148 be set with setsockopt(2) and read with
149 getsockopt(2). The socket option level for IP is
150 __SOL_IP__. A boolean integer flag is zero when it is
151 false, otherwise true.
152
153
154 __IP_OPTIONS__
155
156
157 Sets or get the IP options to be sent with every packet from
158 this socket. The arguments are a pointer to a memory buffer
159 containing the options and the option length. The
160 setsockopt(2) call sets the IP options associated
161 with a socket. The maximum option size for IPv4 is 40 bytes.
162 See RFC791 for the allowed options. When the initial
163 connection request packet for a __SOCK_STREAM__ socket
164 contains IP options, the IP options will be set
165 automatically to the options from the initial packet with
166 routing headers reversed. Incoming packets are not allowed
167 to change options after the connection is established. The
168 processing of all incoming source routing options is
169 disabled by default and can be enabled by using the
170 __accept_source_route__ sysctl. Other options like
171 timestamps are still handled. For datagram sockets, IP
172 options can be only set by the local user. Calling
173 getsockopt(2) with ''IP_OPTIONS'' puts the current
174 IP options used for sending into the supplied
175 buffer.
176
177
178 __IP_PKTINFO__
179
180
181 Pass an ''IP_PKTINFO'' ancillary message that contains a
182 __pktinfo__ structure that supplies some information
183 about the incoming packet. This only works for datagram
184 oriented sockets. The argument is a flag that tells the
185 socket whether the IP_PKTINFO message should be passed or
186 not. The message itself can only be sent/retrieved as
187 control message with a packet using recvmsg(2) or
188 sendmsg(2).
189
190
5 ScottLamb 191 struct in_pktinfo {
192 unsigned int ipi_ifindex; /* Interface index */
193 struct in_addr ipi_spec_dst; /* Local address */
194 struct in_addr ipi_addr; /* Header Destination address */
195 };
1 perry 196
197
198 __ipi_ifindex__ is the unique index of the interface the
199 packet was received on. __ipi_spec_dst__ is the local
200 address of the packet and __ipi_addr__ is the destination
201 address in the packet header. If ''IP_PKTINFO'' is passed
202 to sendmsg(2) then the outgoing packet will be sent
203 over the interface specified in __ipi_ifindex__ with the
204 destination address set to __ipi_spec_dst__
205
206
207 __IP_RECVTOS__
208
209
210 If enabled the ''IP_TOS'' ancillary message is passed
211 with incoming packets. It contains a byte which specifies
212 the Type of Service/Precedence field of the packet header.
213 Expects a boolean integer flag.
214
215
216 __IP_RECVTTL__
217
218
219 When this flag is set pass a ''IP_RECVTTL'' control
220 message with the time to live field of the received packet
221 as a byte. Not supported for __SOCK_STREAM__
222 sockets.
223
224
225 __IP_RECVOPTS__
226
227
228 Pass all incoming IP options to the user in a
229 ''IP_OPTIONS'' control message. The routing header and
230 other options are already filled in for the local host. Not
231 supported for ''SOCK_STREAM'' sockets.
232
233
234 __IP_RETOPTS__
235
236
237 Identical to ''IP_RECVOPTS'' but returns raw unprocessed
238 options with timestamp and route record options not filled
239 in for this hop.
240
241
242 __IP_TOS__
243
244
245 Set or receive the Type-Of-Service (TOS) field that is sent
246 with every IP packet originating from this socket. It is
247 used to prioritize packets on the network. TOS is a byte.
248 There are some standard TOS flags defined:
249 __IPTOS_LOWDELAY__ to minimize delays for interactive
250 traffic, __IPTOS_THROUGHPUT__ to optimize throughput,
251 __IPTOS_RELIABILITY__ to optimize for reliability,
252 __IPTOS_MINCOST__ should be used for
253 __IPTOS_LOWDELAY__ datagrams first by default, but the
254 exact behaviour depends on the configured queueing
255 discipline. Some high priority levels may require an
256 effective user id of 0 or the __CAP_NET_ADMIN__
257 capability. The priority can also be set in a protocol
258 independent way by the ( __SOL_SOCKET, SO_PRIORITY__ )
259 socket option (see socket(7) ).
260
261
262 __IP_TTL__
263
264
265 Set or retrieve the current time to live field that is send
266 in every packet send from this socket.
267
268
269 __IP_HDRINCL__
270
271
272 If enabled the user supplies an ip header in front of the
273 user data. Only valid for __SOCK_RAW__ sockets. See
274 raw(7) for more information. When this flag is
275 enabled the values set by ''IP_OPTIONS'', ''IP_TTL''
276 and ''IP_TOS'' are ignored.
277
278
279 __IP_RECVERR__ (defined in
280 __
281
282
283 Enable extended reliable error message passing. When enabled
284 on a datagram socket all generated errors will be queued in
285 a per-socket error queue. When the user receives an error
286 from a socket operation the errors can be received by
287 calling recvmsg(2) with the __MSG_ERRQUEUE__ flag
288 set. The __sock_extended_err__ structure describing the
289 error will be passed in a ancillary message with the type
290 ''IP_RECVERR'' and the level __SOL_IP__. This is
291 useful for reliable error handling on unconnected sockets.
292 The received data portion of the error queue contains the
293 error packet.
294
295
296 The ''IP_RECVERR'' control message contains a
297 __sock_extended_err__ structure:
298
299
300 #define SO_EE_ORIGIN_NONE 0
301 #define SO_EE_ORIGIN_LOCAL 1
302 #define SO_EE_ORIGIN_ICMP 2
303 #define SO_EE_ORIGIN_ICMP6 3
304 struct sock_extended_err {
305 u_int32_t ee_errno; /* error number */
306 u_int8_t ee_origin; /* where the error originated */
307 u_int8_t ee_type; /* type */
308 u_int8_t ee_code; /* code */
309 u_int8_t ee_pad;
310 u_int32_t ee_info; /* additional information */
311 u_int32_t ee_data; /* other data */
312 /* More data may follow */
313 };
314 struct sockaddr *SO_EE_OFFENDER(struct sock_extended_err *);
315
316
317 __ee_errno__ contains the errno number of the queued
318 error. __ee_origin__ is the origin code of where the
319 error originated. The other fields are protocol specific.
320 The macro __SO_EE_OFFENDER__ returns a pointer to the
321 address of the network object where the error originated
322 from given a pointer to the ancillary message. If this
323 address is not known, the ''sa_family'' member of the
324 __sockaddr__ contains __AF_UNSPEC__ and the other
325 fields of the __sockaddr__ are undefined.
326
327
328 IP uses the __sock_extended_err__ structure as follows:
329 ''ee_origin'' is set to __SO_EE_ORIGIN_ICMP__ for
330 errors received as an ICMP packet, or
331 __SO_EE_ORIGIN_LOCAL__ for locally generated errors.
332 Unknown values should be ignored. ''ee_type'' and
333 ''ee_code'' are set from the type and code fields of the
334 ICMP header. ''ee_info'' contains the discovered MTU for
335 __EMSGSIZE__ errors. The message also contains the
336 ''sockaddr_in of the node'' caused the error, which can
337 be accessed with the __SO_EE_OFFENDER__ macro. The
338 ''sin_family'' field of the SO_EE_OFFENDER address is
339 ''AF_UNSPEC'' when the source was unknown. When the error
340 originated from the network, all IP options
341 (''IP_OPTIONS'', ''IP_TTL'', etc.) enabled on the
342 socket and contained in the error packet are passed as
343 control messages. The payload of the packet causing the
344 error is returned as normal payload. Note that TCP has no
345 error queue; __MSG_ERRQUEUE__ is illegal on
346 __SOCK_STREAM__ sockets. Thus all errors are returned by
347 socket function return or __SO_ERROR__ only.
348
349
350 For raw sockets, ''IP_RECVERR'' enables passing of all
351 received ICMP errors to the application, otherwise errors
352 are only reported on connected sockets
353
354
355 It sets or retrieves an integer boolean flag.
356 ''IP_RECVERR'' defaults to off.
357
358
359 __IP_PMTU_DISCOVER__
360
361
362 Sets or receives the Path MTU Discovery setting for a
363 socket. When enabled, Linux will perform Path MTU Discovery
364 as defined in RFC1191 on this socket. The don't fragment
365 flag is set on all outgoing datagrams. The system-wide
366 default is controlled by the __ip_no_pmtu_disc__ sysctl
367 for __SOCK_STREAM__ sockets, and disabled on all others.
368 For non __SOCK_STREAM__ sockets it is the user's
369 responsibility to packetize the data in MTU sized chunks and
370 to do the retransmits if necessary. The kernel will reject
371 packets that are bigger than the known path MTU if this flag
372 is set (with __EMSGSIZE__ ).
373
374
375 When PMTU discovery is enabled the kernel automatically keeps track of the path MTU per destination host. When it is connected to a specific peer with connect(2) the currently known path MTU can be retrieved conveniently using the __IP_MTU__ socket option (e.g. after a __EMSGSIZE__ error occurred). It may change over time. For connectionless sockets with many destinations the new also MTU for a given destination can also be accessed using the error queue (see __IP_RECVERR__). A new error will be queued for every incoming MTU update.
376
377
378 While MTU discovery is in progress initial packets from
379 datagram sockets may be dropped. Applications using UDP
380 should be aware of this and not take it into account for
381 their packet retransmit strategy.
382
383
384 To bootstrap the path MTU discovery process on unconnected
385 sockets it is possible to start with a big datagram size (up
386 to 64K-headers bytes long) and let it shrink by updates of
387 the path MTU.
388
389
390 To get an initial estimate of the path MTU connect a
391 datagram socket to the destination address using
392 connect(2) and retrieve the MTU by calling
393 getsockopt(2) with the __IP_MTU__
394 option.
395
396
397 __IP_MTU__
398
399
400 Retrieve the current known path MTU of the current socket.
401 Only valid when the socket has been connected. Returns an
402 integer. Only valid as a getsockopt(2).
403
404
405 __IP_ROUTER_ALERT__
406
407
408 Pass all to-be forwarded packets with the IP Router Alert
409 option set to this socket. Only valid for raw sockets. This
410 is useful, for instance, for user space RSVP daemons. The
411 tapped packets are not forwarded by the kernel, it is the
412 users responsibility to send them out again. Socket binding
413 is ignored, such packets are only filtered by protocol.
414 Expects an integer flag.
415
416
417 __IP_MULTICAST_TTL__
418
419
420 Set or reads the time-to-live value of outgoing multicast
421 packets for this socket. It is very important for multicast
422 packets to set the smallest TTL possible. The default is 1
423 which means that multicast packets don't leave the local
424 network unless the user program explicitly requests it.
425 Argument is an integer.
426
427
428 __IP_MULTICAST_LOOP__
429
430
431 Sets or reads a boolean integer argument whether sent
432 multicast packets should be looped back to the local
433 sockets.
434
435
436 __IP_ADD_MEMBERSHIP__
437
438
439 Join a multicast group. Argument is a __struct ip_mreqn__
440 structure.
441
442
5 ScottLamb 443 struct ip_mreqn {
444 struct in_addr imr_multiaddr; /* IP multicast group address */
445 struct in_addr imr_address; /* IP address of local interface */
446 int imr_ifindex; /* interface index */
447 };
1 perry 448
449
450 ''imr_multiaddr'' contains the address of the multicast
451 group the application wants to join or leave. It must be a
452 valid multicast address. ''imr_address'' is the address
453 of the local interface with which the system should join the
454 multicast group; if it is equal to __INADDR_ANY__ an
455 appropriate interface is chosen by the system.
456 ''imr_ifindex'' is the interface index of the interface
457 that should join/leave the ''imr_multiaddr'' group, or 0
458 to indicate any interface.
459
460
461 For compatibility, the old __ip_mreq__ structure is still
462 supported. It differs from __ip_mreqn__ only by not
463 including the ''imr_ifindex'' field. Only valid as a
464 setsockopt(2).
465
466
467 __IP_DROP_MEMBERSHIP__
468
469
470 Leave a multicast group. Argument is an __ip_mreqn__ or
471 __ip_mreq__ structure similar to
472 ''IP_ADD_MEMBERSHIP''.
473
474
475 __IP_MULTICAST_IF__
476
477
478 Set the local device for a multicast socket. Argument is an
479 __ip_mreqn__ or __ip_mreq__ structure similar to
480 ''IP_ADD_MEMBERSHIP''.
481
482
483 When an invalid socket option is passed, __ENOPROTOOPT__
484 is returned.
485 !!SYSCTLS
486
487
488 The IP protocol supports the sysctl interface to configure
489 some global options. The sysctls can be accessed by reading
490 or writing the __/proc/sys/net/ipv4/*__ files or using
491 the sysctl(2) interface.
492
493
494 __ip_default_ttl__
495
496
497 Set the default time-to-live value of outgoing packets. This
498 can be changed per socket with the ''IP_TTL''
499 option.
500
501
502 __ip_forward__
503
504
505 Enable IP forwarding with a boolean flag. IP forwarding can
506 be also set on a per interface basis.
507
508
509 __ip_dynaddr__
510
511
512 Enable dynamic socket address and masquerading entry
513 rewriting on interface address change. This is useful for
514 dialup interface with changing IP addresses. 0 means no
515 rewriting, 1 turns it on and 2 enables verbose
516 mode.
517
518
519 __ip_autoconfig__
520
521
522 Not documented.
523
524
525 __ip_local_port_range__
526
527
528 Contains two integers that define the default local port
529 range allocated to sockets. Allocation starts with the first
530 number and ends with the second number. Note that these
531 should not conflict with the ports used by masquerading
532 (although the case is handled). Also arbitary choices may
533 cause problems with some firewall packet filters that make
534 assumptions about the local ports in use. First number
535 should be at least
536
537
538 __ip_no_pmtu_disc__
539
540
541 If enabled, don't do Path MTU Discovery for TCP sockets by
542 default. Path MTU discovery may fail if misconfigured
543 firewalls (that drop all ICMP packets) or misconfigured
544 interfaces (e.g., a point-to-point link where the both ends
545 don't agree on the MTU) are on the path. It is better to fix
546 the broken routers on the path than to turn off Path MTU
547 Discovery globally, because not doing it incurs a high cost
548 to the network.
549
550
551 __ipfrag_high_thresh, ipfrag_low_thresh__
552
553
554 If the amount of queued IP fragments reaches
555 __ipfrag_high_thresh ,__ the queue is pruned down to
556 __ipfrag_low_thresh .__ Contains an integer with the
557 number of bytes.
558
559
560 __ip_always_defrag__
561
562
563 [[New with Kernel 2.2.13; in earlier kernel version the
564 feature was controlled at compile time by the
565 __CONFIG_IP_ALWAYS_DEFRAG__ option]
566
567
568 When this boolean frag is enabled (not equal 0) incoming
569 fragments (parts of IP packets that arose when some host
570 between origin and destination decided that the packets were
571 too large and cut them into pieces) will be reassembled
572 (defragmented) before being processed, even if they are
573 about to be forwarded.
574
575
576 Only enable if running either a firewall that is the sole
577 link to your network or a transparent proxy; never ever turn
578 on here for a normal router or host. Otherwise fragmented
579 communication may me disturbed when the fragments would
580 travel over different links. Defragmentation also has a
581 large memory and CPU time cost.
582
583
584 This is automagically turned on when masquerading or
585 transparent proxying are configured.
586
587
588 __neigh/*__
589
590
591 See arp(7).
592 !!IOCTLS
593
594
595 All ioctls described in socket(7) apply to
596 ip.
597
598
599 The ioctls to configure firewalling are documented in
600 ipfw(7) from the __ipchains__
601 package.
602
603
604 Ioctls to configure generic device parameters are described
605 in netdevice(7).
606 !!NOTES
607
608
609 Be very careful with the __SO_BROADCAST__ option - it is
610 not privileged in Linux. It is easy to overload the network
611 with careless broadcasts. For new application protocols it
612 is better to use a multicast group instead of broadcasting.
613 Broadcasting is discouraged.
614
615
616 Some other BSD sockets implementations provide
617 ''IP_RCVDSTADDR'' and ''IP_RECVIF'' socket options to
618 get the destination address and the interface of received
619 datagrams. Linux has the more general ''IP_PKTINFO'' for
620 the same task.
621 !!ERRORS
622
623
624 __ENOTCONN__
625
626
627 The operation is only defined on a connected socket, but the
628 socket wasn't connected.
629
630
631 __EINVAL__
632
633
634 Invalid argument passed. For send operations this can be
635 caused by sending to a ''blackhole'' route.
636
637
638 __EMSGSIZE__
639
640
641 Datagram is bigger than an MTU on the path and it cannot be
642 fragmented.
643
644
645 __EACCES__
646
647
648 The user tried to execute an operation without the necessary
649 permissions. These include: Sending a packet to a broadcast
650 address without having the __SO_BROADCAST__ flag set.
651 Sending a packet via a ''prohibit'' route. Modifying
652 firewall settings without __CAP_NET_ADMIN__ or effective
653 user id 0. Binding to a reserved port without the
654 __CAP_NET_BIND_SERVICE__ capacibility or effective user
655 id 0.
656
657
658 __EADDRINUSE__
659
660
661 Tried to bind to an address already in use.
662
663
664 __ENOPROTOOPT__ and __EOPNOTSUPP__
665
666
667 Invalid socket option passed.
668
669
670 __EPERM__
671
672
673 User doesn't have permission to set high priority, change
674 configuration, or send signals to the requested process or
675 group,
676
677
678 __EADDRNOTAVAIL__
679
680
681 A non-existent interface was requested or the requested
682 source address was not local.
683
684
685 __EAGAIN__
686
687
688 Operation on a non-blocking socket would block.
689
690
691 __ESOCKTNOSUPPORT__
692
693
694 The socket is not configured or an unknown socket type was
695 requested.
696
697
698 __EISCONN__
699
700
701 connect(2) was called on an already connected
702 socket.
703
704
705 __EALREADY__
706
707
708 An connection operation on a non-blocking socket is already
709 in progress.
710
711
712 __ECONNABORTED__
713
714
715 A connection was closed during an
716 accept(2).
717
718
719 __EPIPE__
720
721
722 The connection was unexpectedly closed or shut down by the
723 other end.
724
725
726 __ENOENT__
727
728
729 __SIOCGSTAMP__ was called on a socket where no packet
730 arrived.
731
732
733 __EHOSTUNREACH__
734
735
736 No valid routing table entry matches the destination
737 address. This error can be caused by a ICMP message from a
738 remote router or for the local routing table.
739
740
741 __ENODEV__
742
743
744 Network device not available or not capable of sending
745 IP.
746
747
748 __ENOPKG__
749
750
751 A kernel subsystem was not configured.
752
753
754 __ENOBUFS, ENOMEM__
755
756
757 Not enough free memory. This often means that the memory
758 allocation is limited by the socket buffer limits, not by
759 the system memory, but this is not 100%
760 consistent.
761
762
763 Other errors may be generated by the overlaying protocols;
764 see tcp(7), raw(7), udp(7) and
765 socket(7).
766 !!VERSIONS
767
768
769 ''IP_PKTINFO'', ''IP_MTU'', ''IP_PMTU_DISCOVER'',
770 ''IP_PKTINFO'', ''IP_RECVERR'' and
771 ''IP_ROUTER_ALERT'' are new options in Linux 2.2. They
772 are also all Linux specific and should not be used in
773 programs intended to be portable.
774
775
776 __struct ip_mreqn__ is new in Linux 2.2. Linux 2.0 only
777 supported __ip_mreq__.
778
779
780 The sysctls were introduced with Linux 2.2.
781 !!COMPATIBILITY
782
783
784 For compatibility with Linux 2.0, the obsolete
785 __socket(PF_INET, SOCK_RAW,__ ''protocol''__)__
786 syntax is still supported to open a packet(7) socket.
787 This is deprecated and should be replaced by
788 __socket(PF_PACKET, SOCK_RAW,__ ''protocol''__)__
789 instead. The main difference is the new __sockaddr_ll__
790 address structure for generic link layer information instead
791 of the old __sockaddr_pkt__.
792 !!BUGS
793
794
795 There are too many inconsistent error values.
796
797
798 The ioctls to configure IP-specific interface options and
799 ARP tables are not described.
800
801
802 Some versions of glibc forget to declare ''in_pktinfo.''
803 Workaround currently is to copy it into your program from
804 this man page.
805
806
807 Receiving the original destination address with
808 __MSG_ERRQUEUE__ in ''msg_name'' by recvmsg(2)
809 does not work in some 2.2 kernels.
810 !!AUTHORS
811
812
813 This man page was written by Andi Kleen.
814 !!SEE ALSO
815
816
817 sendmsg(2), recvmsg(2), socket(7),
818 netlink(7), tcp(7), udp(7),
819 raw(7), ipfw(7)
820
821
822 RFC791 for the original IP specification.
823 RFC1122 for the IPv4 host requirements.
824 RFC1812 for the IPv4 router requirements.
825 ----
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