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22 .TH PCAP 3 "27 February 2004"
24 pcap \- Packet Capture library
33 char errbuf[PCAP_ERRBUF_SIZE];
37 pcap_t *pcap_open_live(const char *device, int snaplen,
39 int promisc, int to_ms, char *errbuf)
40 pcap_t *pcap_open_dead(int linktype, int snaplen)
41 pcap_t *pcap_open_offline(const char *fname, char *errbuf)
42 pcap_t *pcap_fopen_offline(FILE *fp, char *errbuf)
43 pcap_dumper_t *pcap_dump_open(pcap_t *p, const char *fname)
44 pcap_dumper_t *pcap_dump_fopen(pcap_t *p, FILE *fp)
48 int pcap_setnonblock(pcap_t *p, int nonblock, char *errbuf);
49 int pcap_getnonblock(pcap_t *p, char *errbuf);
53 int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf)
54 void pcap_freealldevs(pcap_if_t *alldevs)
55 char *pcap_lookupdev(char *errbuf)
56 int pcap_lookupnet(const char *device, bpf_u_int32 *netp,
58 bpf_u_int32 *maskp, char *errbuf)
62 typedef void (*pcap_handler)(u_char *user, const struct pcap_pkthdr *h,
66 int pcap_dispatch(pcap_t *p, int cnt,
68 pcap_handler callback, u_char *user)
69 int pcap_loop(pcap_t *p, int cnt,
71 pcap_handler callback, u_char *user)
72 void pcap_dump(u_char *user, struct pcap_pkthdr *h,
78 int pcap_compile(pcap_t *p, struct bpf_program *fp,
80 char *str, int optimize, bpf_u_int32 netmask)
81 int pcap_setfilter(pcap_t *p, struct bpf_program *fp)
82 void pcap_freecode(struct bpf_program *)
83 int pcap_setdirection(pcap_t *p, pcap_direction_t d)
87 const u_char *pcap_next(pcap_t *p, struct pcap_pkthdr *h)
88 int pcap_next_ex(pcap_t *p, struct pcap_pkthdr **pkt_header,
90 const u_char **pkt_data)
94 void pcap_breakloop(pcap_t *)
98 int pcap_inject(pcap_t *p, const void *buf, size_t size)
99 int pcap_sendpacket(pcap_t *p, const u_char *buf, int size)
103 int pcap_datalink(pcap_t *p)
104 int pcap_list_datalinks(pcap_t *p, int **dlt_buf);
105 int pcap_set_datalink(pcap_t *p, int dlt);
106 int pcap_datalink_name_to_val(const char *name);
107 const char *pcap_datalink_val_to_name(int dlt);
108 const char *pcap_datalink_val_to_description(int dlt);
109 int pcap_snapshot(pcap_t *p)
110 int pcap_is_swapped(pcap_t *p)
111 int pcap_major_version(pcap_t *p)
112 int pcap_minor_version(pcap_t *p)
113 int pcap_stats(pcap_t *p, struct pcap_stat *ps)
114 FILE *pcap_file(pcap_t *p)
115 int pcap_fileno(pcap_t *p)
116 int pcap_get_selectable_fd(pcap_t *p);
117 void pcap_perror(pcap_t *p, char *prefix)
118 char *pcap_geterr(pcap_t *p)
119 char *pcap_strerror(int error)
120 const char *pcap_lib_version(void)
124 void pcap_close(pcap_t *p)
125 int pcap_dump_flush(pcap_dumper_t *p)
126 long pcap_dump_ftell(pcap_dumper_t *p)
127 FILE *pcap_dump_file(pcap_dumper_t *p)
128 void pcap_dump_close(pcap_dumper_t *p)
132 The Packet Capture library
133 provides a high level interface to packet capture systems. All packets
134 on the network, even those destined for other hosts, are accessible
135 through this mechanism.
141 .BR pcap_open_live() ,
142 .BR pcap_open_dead() ,
143 .BR pcap_open_offline() ,
144 .BR pcap_fopen_offline() ,
145 .BR pcap_setnonblock() ,
146 .BR pcap_getnonblock() ,
147 .BR pcap_findalldevs() ,
148 .BR pcap_lookupdev() ,
151 is assumed to be able to hold at least
156 is used to obtain a packet capture descriptor to look
157 at packets on the network.
159 is a string that specifies the network device to open; on Linux systems
160 with 2.2 or later kernels, a
164 can be used to capture packets from all interfaces.
166 specifies the maximum number of bytes to capture. If this value is less
167 than the size of a packet that is captured, only the first
169 bytes of that packet will be captured and provided as packet data. A
170 value of 65535 should be sufficient, on most if not all networks, to
171 capture all the data available from the packet.
173 specifies if the interface is to be put into promiscuous mode.
174 (Note that even if this parameter is false, the interface
175 could well be in promiscuous mode for some other reason.) For now, this
176 doesn't work on the "any" device; if an argument of "any" or NULL is
181 specifies the read timeout in milliseconds. The read timeout is used to
182 arrange that the read not necessarily return immediately when a packet
183 is seen, but that it wait for some amount of time to allow more packets
184 to arrive and to read multiple packets from the OS kernel in one
185 operation. Not all platforms support a read timeout; on platforms that
186 don't, the read timeout is ignored. A zero value for
188 on platforms that support a read timeout,
189 will cause a read to wait forever to allow enough packets to
190 arrive, with no timeout.
192 is used to return error or warning text. It will be set to error text when
197 may also be set to warning text when
199 succeds; to detect this case the caller should store a zero-length string in
203 and display the warning to the user if
205 is no longer a zero-length string.
208 is used for creating a
210 structure to use when calling the other functions in libpcap. It is
211 typically used when just using libpcap for compiling BPF code.
213 .B pcap_open_offline()
214 is called to open a ``savefile'' for reading.
216 specifies the name of the file to open. The file has
217 the same format as those used by
221 The name "-" in a synonym for
223 Alternatively, you may call
224 .B pcap_fopen_offline()
225 to read dumped data from an existing open stream
227 Note that on Windows, that stream should be opened in binary mode.
229 is used to return error text and is only set when
230 .B pcap_open_offline()
232 .B pcap_fopen_offline()
237 is called to open a ``savefile'' for writing. The name "-" in a synonym
241 is returned on failure.
245 struct as returned by
246 .B pcap_open_offline()
248 .BR pcap_open_live() .
250 specifies the name of the file to open. Alternatively, you may call
252 to write data to an existing open stream
254 Note that on Windows, that stream should be opened in binary mode.
259 can be used to get the error text.
262 .B pcap_setnonblock()
263 puts a capture descriptor, opened with
264 .BR pcap_open_live() ,
265 into ``non-blocking'' mode, or takes it out of ``non-blocking'' mode,
266 depending on whether the
268 argument is non-zero or zero. It has no effect on ``savefiles''.
269 If there is an error, \-1 is returned and
271 is filled in with an appropriate error message; otherwise, 0 is
274 ``non-blocking'' mode, an attempt to read from the capture descriptor
277 will, if no packets are currently available to be read, return 0
278 immediately rather than blocking waiting for packets to arrive.
282 will not work in ``non-blocking'' mode.
284 .B pcap_getnonblock()
285 returns the current ``non-blocking'' state of the capture descriptor; it
286 always returns 0 on ``savefiles''.
287 If there is an error, \-1 is returned and
289 is filled in with an appropriate error message.
291 .B pcap_findalldevs()
292 constructs a list of network devices that can be opened with
293 .BR pcap_open_live() .
294 (Note that there may be network devices that cannot be opened with
298 .BR pcap_findalldevs() ,
299 because, for example, that process might not have sufficient privileges
300 to open them for capturing; if so, those devices will not appear on the
303 is set to point to the first element of the list; each element of the
306 and has the following members:
312 a pointer to the next element in the list;
314 for the last element of the list
317 a pointer to a string giving a name for the device to pass to
323 a pointer to a string giving a human-readable description of the device
326 a pointer to the first element of a list of addresses for the interface
333 set if the interface is a loopback interface
337 Each element of the list of addresses is of type
339 and has the following members:
345 a pointer to the next element in the list;
347 for the last element of the list
352 containing an address
359 that contains the netmask corresponding to the address pointed to by
367 that contains the broadcast address corresponding to the address pointed
370 may be null if the interface doesn't support broadcasts
377 that contains the destination address corresponding to the address pointed
380 may be null if the interface isn't a point-to-point interface
383 Note that not all the addresses in the list of addresses are
384 necessarily IPv4 or IPv6 addresses - you must check the
388 before interpreting the contents of the address.
391 is returned on failure, in which case
393 is filled in with an appropriate error message;
395 is returned on success.
397 .B pcap_freealldevs()
398 is used to free a list allocated by
399 .BR pcap_findalldevs() .
402 returns a pointer to a network device suitable for use with
405 .BR pcap_lookupnet() .
406 If there is an error,
410 is filled in with an appropriate error message.
413 is used to determine the network number and mask
414 associated with the network device
423 A return of \-1 indicates an error in which case
425 is filled in with an appropriate error message.
428 is used to collect and process packets.
430 specifies the maximum number of packets to process before returning.
431 This is not a minimum number; when reading a live capture, only one
432 bufferful of packets is read at a time, so fewer than
434 packets may be processed. A
436 of \-1 processes all the packets received in one buffer when reading a
437 live capture, or all the packets in the file when reading a
440 specifies a routine to be called with three arguments:
443 pointer which is passed in from
444 .BR pcap_dispatch() ,
446 .I const struct pcap_pkthdr
447 pointer to a structure with the following members:
453 containing the time when the packet was captured
458 giving the number of bytes of the packet that are available from the
464 giving the length of the packet, in bytes (which might be more than the
465 number of bytes available from the capture, if the length of the packet
466 is larger than the maximum number of bytes to capture)
474 .I struct pcap_pkthdr
475 a pointer to which is passed to the callback routine)
476 bytes of data from the packet (which won't necessarily be the entire
477 packet; to capture the entire packet, you will have to provide a value
482 that is sufficiently large to get all of the packet's data - a value of
483 65535 should be sufficient on most if not all networks).
485 The number of packets read is returned.
486 0 is returned if no packets were read from a live capture (if, for
487 example, they were discarded because they didn't pass the packet filter,
488 or if, on platforms that support a read timeout that starts before any
489 packets arrive, the timeout expires before any packets arrive, or if the
490 file descriptor for the capture device is in non-blocking mode and no
491 packets were available to be read) or if no more packets are available
492 in a ``savefile.'' A return of \-1 indicates
493 an error in which case
497 may be used to display the error text.
498 A return of \-2 indicates that the loop terminated due to a call to
500 before any packets were processed.
502 If your application uses pcap_breakloop(),
503 make sure that you explicitly check for \-1 and \-2, rather than just
504 checking for a return value < 0.
508 when reading a live capture,
510 will not necessarily return when the read times out; on some platforms,
511 the read timeout isn't supported, and, on other platforms, the timer
512 doesn't start until at least one packet arrives. This means that the
515 be used in, for example, an interactive application, to allow the packet
516 capture loop to ``poll'' for user input periodically, as there's no
519 will return after the timeout expires.
524 except it keeps reading packets until
526 packets are processed or an error occurs.
529 return when live read timeouts occur.
530 Rather, specifying a non-zero read timeout to
534 allows the reception and processing of any packets that arrive when the
540 to loop forever (or at least until an error occurs). \-1 is returned on
541 an error; 0 is returned if
543 is exhausted; \-2 is returned if the loop terminated due to a call to
545 before any packets were processed.
547 If your application uses pcap_breakloop(),
548 make sure that you explicitly check for \-1 and \-2, rather than just
549 checking for a return value < 0.
553 reads the next packet (by calling
559 pointer to the data in that packet. (The
561 struct for that packet is not supplied.)
563 is returned if an error occured, or if no packets were read from a live
564 capture (if, for example, they were discarded because they didn't pass
565 the packet filter, or if, on platforms that support a read timeout that
566 starts before any packets arrive, the timeout expires before any packets
567 arrive, or if the file descriptor for the capture device is in
568 non-blocking mode and no packets were available to be read), or if no
569 more packets are available in a ``savefile.'' Unfortunately, there is
570 no way to determine whether an error occured or not.
573 reads the next packet and returns a success/failure indication:
577 the packet was read without problems
580 packets are being read from a live capture, and the timeout expired
583 an error occurred while reading the packet
586 packets are being read from a ``savefile'', and there are no more
587 packets to read from the savefile.
590 If the packet was read without problems, the pointer pointed to by the
592 argument is set to point to the
594 struct for the packet, and the
595 pointer pointed to by the
597 argument is set to point to the data in the packet.
600 sets a flag that will force
604 to return rather than looping; they will return the number of packets
605 that have been processed so far, or \-2 if no packets have been
608 This routine is safe to use inside a signal handler on UNIX or a console
609 control handler on Windows, as it merely sets a flag that is checked
612 The flag is checked in loops reading packets from the OS - a signal by
613 itself will not necessarily terminate those loops - as well as in loops
614 processing a set of packets returned by the OS.
616 Note that if you are catching signals on UNIX systems that support
617 restarting system calls after a signal, and calling pcap_breakloop()
618 in the signal handler, you must specify, when catching those signals,
619 that system calls should NOT be restarted by that signal. Otherwise,
620 if the signal interrupted a call reading packets in a live capture,
621 when your signal handler returns after calling pcap_breakloop(), the
622 call will be restarted, and the loop will not terminate until more
623 packets arrive and the call completes.
625 Note also that, in a multi-threaded application, if one thread is
627 .BR pcap_dispatch() ,
634 in a different thread will not unblock that thread; you will need to use
635 whatever mechanism the OS provides for breaking a thread out of blocking
636 calls in order to unblock the thread, such as thread cancellation in
637 systems that support POSIX threads.
642 will, on some platforms, loop reading packets from the OS; that loop
643 will not necessarily be terminated by a signal, so
645 should be used to terminate packet processing even if
650 does not guarantee that no further packets will be processed by
654 after it is called; at most one more packet might be processed.
656 If \-2 is returned from
660 the flag is cleared, so a subsequent call will resume reading packets.
661 If a positive number is returned, the flag is not cleared, so a
662 subsequent call will return \-2 and clear the flag.
665 sends a raw packet through the network interface;
667 points to the data of the packet, including the link-layer header, and
669 is the number of bytes in the packet.
670 It returns the number of bytes written on success. A return of \-1
671 indicates an error in which case
675 may be used to display the error text.
676 Note that, even if you successfully open the network interface, you
677 might not have permission to send packets on it, or it might not support
680 doesn't have a flag to indicate whether to open for capturing, sending,
681 or capturing and sending, you cannot request an open that supports
682 sending and be notified at open time whether sending will be possible.
683 Note also that some devices might not support sending packets.
685 Note that, on some platforms, the link-layer header of the packet that's
686 sent might not be the same as the link-layer header of the packet
689 as the source link-layer address, if the header contains such an
690 address, might be changed to be the address assigned to the interface on
691 which the packet it sent, if the platform doesn't support sending
692 completely raw and unchanged packets.
697 but it returns 0 on success and \-1 on failure.
701 comes from WinPcap. Both are provided for compatibility.)
704 outputs a packet to the ``savefile'' opened with
705 .BR pcap_dump_open() .
706 Note that its calling arguments are suitable for use with
710 If called directly, the
715 .BR pcap_dump_open() .
718 is used to compile the string
720 into a filter program.
724 struct and is filled in by
727 controls whether optimization on the resulting code is performed.
729 specifies the IPv4 netmask of the network on which packets are being
730 captured; it is used only when checking for IPv4 broadcast addresses in
731 the filter program. If the netmask of the network on which packets are
732 being captured isn't known to the program, or if packets are being
733 captured on the Linux "any" pseudo-interface that can capture on more
734 than one network, a value of 0 can be supplied; tests for IPv4 broadcast
735 addreses won't be done correctly, but all other tests in the filter
736 program will be OK. A return of \-1 indicates an error in which case
738 may be used to display the error text.
740 .B pcap_compile_nopcap()
743 except that instead of passing a pcap structure, one passes the
744 snaplen and linktype explicitly. It is intended to be used for
745 compiling filters for direct BPF usage, without necessarily having
748 A return of \-1 indicates an error; the error text is unavailable.
749 .RB ( pcap_compile_nopcap()
751 .BR pcap_open_dead() ,
755 the latter three routines can be used directly in order to get the error
756 text for a compilation error.)
760 is used to specify a filter program.
764 struct, usually the result of a call to
767 is returned on failure, in which case
769 may be used to display the error text;
771 is returned on success.
774 is used to free up allocated memory pointed to by a
778 when that BPF program is no longer needed, for example after it
779 has been made the filter program for a pcap structure by a call to
780 .BR pcap_setfilter() .
782 .B pcap_setdirection()
783 is used to specify a direction that packets will be captured.
785 is one of the constants
791 will only capture packets received by the device,
793 will only capture packets sent by the device and
795 will capture packets received by or sent by the device.
797 is the default setting if this function is not called. This isn't
798 necessarily supported on all platforms; some platforms might return an
799 error, and some other platforms might not support
801 This operation is not supported if a ``savefile'' is being read.
803 is returned on failure,
805 is returned on success.
808 returns the link layer type; link layer types it can return include:
813 BSD loopback encapsulation; the link layer header is a 4-byte field, in
815 byte order, containing a PF_ value from
817 for the network-layer protocol of the packet.
819 Note that ``host byte order'' is the byte order of the machine on which
820 the packets are captured, and the PF_ values are for the OS of the
821 machine on which the packets are captured; if a live capture is being
822 done, ``host byte order'' is the byte order of the machine capturing the
823 packets, and the PF_ values are those of the OS of the machine capturing
824 the packets, but if a ``savefile'' is being read, the byte order and PF_
827 necessarily those of the machine reading the capture file.
830 Ethernet (10Mb, 100Mb, 1000Mb, and up)
833 IEEE 802.5 Token Ring
839 SLIP; the link layer header contains, in order:
842 a 1-byte flag, which is 0 for packets received by the machine and 1 for
843 packets sent by the machine;
845 a 1-byte field, the upper 4 bits of which indicate the type of packet,
850 an unmodified IP datagram (TYPE_IP);
853 an uncompressed-TCP IP datagram (UNCOMPRESSED_TCP), with that byte being
854 the first byte of the raw IP header on the wire, containing the
855 connection number in the protocol field;
858 a compressed-TCP IP datagram (COMPRESSED_TCP), with that byte being the
859 first byte of the compressed TCP/IP datagram header;
862 for UNCOMPRESSED_TCP, the rest of the modified IP header, and for
863 COMPRESSED_TCP, the compressed TCP/IP datagram header;
867 for a total of 16 bytes; the uncompressed IP datagram follows the header.
871 PPP; if the first 2 bytes are 0xff and 0x03, it's PPP in HDLC-like
872 framing, with the PPP header following those two bytes, otherwise it's
873 PPP without framing, and the packet begins with the PPP header.
879 RFC 1483 LLC/SNAP-encapsulated ATM; the packet begins with an IEEE 802.2
883 raw IP; the packet begins with an IP header.
886 PPP in HDLC-like framing, as per RFC 1662, or Cisco PPP with HDLC
887 framing, as per section 4.3.1 of RFC 1547; the first byte will be 0xFF
888 for PPP in HDLC-like framing, and will be 0x0F or 0x8F for Cisco PPP
892 PPPoE; the packet begins with a PPPoE header, as per RFC 2516.
895 Cisco PPP with HDLC framing, as per section 4.3.1 of RFC 1547.
898 IEEE 802.11 wireless LAN
904 OpenBSD loopback encapsulation; the link layer header is a 4-byte field, in
906 byte order, containing a PF_ value from OpenBSD's
908 for the network-layer protocol of the packet.
910 Note that, if a ``savefile'' is being read, those PF_ values are
912 necessarily those of the machine reading the capture file.
915 Linux "cooked" capture encapsulation; the link layer header contains, in
919 a 2-byte "packet type", in network byte order, which is one of:
923 packet was sent to us by somebody else
926 packet was broadcast by somebody else
929 packet was multicast, but not broadcast, by somebody else
932 packet was sent by somebody else to somebody else
935 packet was sent by us
938 a 2-byte field, in network byte order, containing a Linux ARPHRD_ value
939 for the link layer device type;
941 a 2-byte field, in network byte order, containing the length of the
942 link layer address of the sender of the packet (which could be 0);
944 an 8-byte field containing that number of bytes of the link layer header
945 (if there are more than 8 bytes, only the first 8 are present);
947 a 2-byte field containing an Ethernet protocol type, in network byte
948 order, or containing 1 for Novell 802.3 frames without an 802.2 LLC
949 header or 4 for frames beginning with an 802.2 LLC header.
953 Apple LocalTalk; the packet begins with an AppleTalk LLAP header.
956 OpenBSD pflog; the link layer header contains, in order:
959 a 1-byte header length, in host byte order;
961 a 4-byte PF_ value, in host byte order;
963 a 2-byte action code, in network byte order, which is one of:
976 a 2-byte reason code, in network byte order, which is one of:
998 a 16-character interface name;
1000 a 16-character ruleset name (only meaningful if subrule is set);
1002 a 4-byte rule number, in network byte order;
1004 a 4-byte subrule number, in network byte order;
1006 a 1-byte direction, in network byte order, which is one of:
1010 incoming or outgoing
1021 Prism monitor mode information followed by an 802.11 header.
1024 RFC 2625 IP-over-Fibre Channel, with the link-layer header being the
1025 Network_Header as described in that RFC.
1028 SunATM devices; the link layer header contains, in order:
1031 a 1-byte flag field, containing a direction flag in the uppermost bit,
1032 which is set for packets transmitted by the machine and clear for
1033 packets received by the machine, and a 4-byte traffic type in the
1034 low-order 4 bits, which is one of:
1044 LLC-encapsulated traffic
1061 a 2-byte VCI field, in network byte order.
1064 .B DLT_IEEE802_11_RADIO
1065 link-layer information followed by an 802.11 header - see
1066 http://www.shaftnet.org/~pizza/software/capturefrm.txt for a description
1067 of the link-layer information.
1070 ARCNET, with no exception frames, reassembled packets rather than raw
1071 frames, and an extra 16-bit offset field between the destination host
1075 Linux-IrDA packets, with a
1077 header followed by the IrLAP header.
1080 .B pcap_list_datalinks()
1081 is used to get a list of the supported data link types of the interface
1082 associated with the pcap descriptor.
1083 .B pcap_list_datalinks()
1084 allocates an array to hold the list and sets
1086 The caller is responsible for freeing the array.
1088 is returned on failure;
1089 otherwise, the number of data link types in the array is returned.
1091 .B pcap_set_datalink()
1092 is used to set the current data link type of the pcap descriptor
1093 to the type specified by
1096 is returned on failure.
1098 .B pcap_datalink_name_to_val()
1099 translates a data link type name, which is a
1103 removed, to the corresponding data link type value. The translation
1104 is case-insensitive.
1106 is returned on failure.
1108 .B pcap_datalink_val_to_name()
1109 translates a data link type value to the corresponding data link type
1110 name. NULL is returned on failure.
1112 .B pcap_datalink_val_to_description()
1113 translates a data link type value to a short description of that data
1114 link type. NULL is returned on failure.
1117 returns the snapshot length specified when
1121 .B pcap_is_swapped()
1122 returns true if the current ``savefile'' uses a different byte order
1123 than the current system.
1125 .B pcap_major_version()
1126 returns the major number of the file format of the savefile;
1127 .B pcap_minor_version()
1128 returns the minor number of the file format of the savefile. The
1129 version number is stored in the header of the savefile.
1132 returns the standard I/O stream of the ``savefile,'' if a ``savefile''
1134 .BR pcap_open_offline() ,
1135 or NULL, if a network device was opened with
1136 .BR pcap_open_live() .
1139 returns 0 and fills in a
1141 struct. The values represent packet statistics from the start of the
1142 run to the time of the call. If there is an error or the underlying
1143 packet capture doesn't support packet statistics, \-1 is returned and
1144 the error text can be obtained with
1149 is supported only on live captures, not on ``savefiles''; no statistics
1150 are stored in ``savefiles'', so no statistics are available when reading
1151 from a ``savefile''.
1154 returns the file descriptor number from which captured packets are read,
1155 if a network device was opened with
1156 .BR pcap_open_live() ,
1157 or \-1, if a ``savefile'' was opened with
1158 .BR pcap_open_offline() .
1160 .B pcap_get_selectable_fd()
1161 returns, on UNIX, a file descriptor number for a file descriptor on
1167 to wait for it to be possible to read packets without blocking, if such
1168 a descriptor exists, or \-1, if no such descriptor exists. Some network
1175 (for example, regular network devices on FreeBSD 4.3 and 4.4, and Endace
1176 DAG devices), so \-1 is returned for those devices.
1178 Note that on most versions of most BSDs (including Mac OS X)
1182 do not work correctly on BPF devices;
1183 .B pcap_get_selectable_fd()
1184 will return a file descriptor on most of those versions (the exceptions
1185 being FreeBSD 4.3 and 4.4), a simple
1189 will not return even after a timeout specified in
1191 expires. To work around this, an application that uses
1195 to wait for packets to arrive must put the
1197 in non-blocking mode, and must arrange that the
1201 have a timeout less than or equal to the timeout specified in
1202 .BR pcap_open_live() ,
1203 and must try to read packets after that timeout expires, regardless of
1208 indicated that the file descriptor for the
1210 is ready to be read or not. (That workaround will not work in FreeBSD
1211 4.3 and later; however, in FreeBSD 4.6 and later,
1215 work correctly on BPF devices, so the workaround isn't necessary,
1216 although it does no harm.)
1218 .B pcap_get_selectable_fd()
1219 is not available on Windows.
1222 prints the text of the last pcap library error on
1228 returns the error text pertaining to the last pcap library error.
1230 the pointer it returns will no longer point to a valid error message
1233 passed to it is closed; you must use or copy the string before closing
1242 .B pcap_lib_version()
1243 returns a pointer to a string giving information about the version of
1244 the libpcap library being used; note that it contains more information
1245 than just a version number.
1248 closes the files associated with
1250 and deallocates resources.
1253 returns the standard I/O stream of the ``savefile'' opened by
1254 .BR pcap_dump_open().
1256 .B pcap_dump_flush()
1257 flushes the output buffer to the ``savefile,'' so that any packets
1260 but not yet written to the ``savefile'' will be written.
1262 is returned on error, 0 on success.
1264 .B pcap_dump_ftell()
1265 returns the current file position for the ``savefile'', representing the
1266 number of bytes written by
1271 is returned on error.
1273 .B pcap_dump_close()
1274 closes the ``savefile.''
1277 tcpdump(1), tcpslice(1)
1279 The original authors are:
1283 Steven McCanne, all of the
1284 Lawrence Berkeley National Laboratory, University of California, Berkeley, CA.
1286 The current version is available from "The Tcpdump Group"'s Web site at
1289 .I http://www.tcpdump.org/
1292 Please send problems, bugs, questions, desirable enhancements, etc. to:
1295 tcpdump-workers@tcpdump.org
1298 Please send source code contributions, etc. to:
projects / libpcap / blob