svcadm(1M)을 검색하려면 섹션에서 1M 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.
pcap_dispatch(3pcap)
PCAP_LOOP(3pcap)PCAP_LOOP(3pcap)
NAME
pcap_loop, pcap_dispatch - process packets from a live capture or save‐
file
SYNOPSIS
#include <pcap/pcap.h>
typedef void (*pcap_handler)(u_char *user, const struct pcap_pkthdr *h,
const u_char *bytes);
int pcap_loop(pcap_t *p, int cnt,
pcap_handler callback, u_char *user);
int pcap_dispatch(pcap_t *p, int cnt,
pcap_handler callback, u_char *user);
DESCRIPTION
pcap_loop() processes packets from a live capture or ``savefile'' until
cnt packets are processed, the end of the ``savefile'' is reached when
reading from a ``savefile'', pcap_breakloop(3PCAP) is called, or an
error occurs. It does not return when live packet buffer timeouts
occur. A value of -1 or 0 for cnt is equivalent to infinity, so that
packets are processed until another ending condition occurs.
pcap_dispatch() processes packets from a live capture or ``savefile''
until cnt packets are processed, the end of the current bufferful of
packets is reached when doing a live capture, the end of the ``save‐
file'' is reached when reading from a ``savefile'', pcap_breakloop() is
called, or an error occurs. Thus, when doing a live capture, cnt is
the maximum number of packets to process before returning, but is not a
minimum number; when reading a live capture, only one bufferful of
packets is read at a time, so fewer than cnt packets may be processed.
A value of -1 or 0 for cnt causes all the packets received in one buf‐
fer to be processed when reading a live capture, and causes all the
packets in the file to be processed when reading a ``savefile''.
Note that, when doing a live capture on some platforms, if the read
timeout expires when there are no packets available, pcap_dispatch()
will return 0, even when not in non-blocking mode, as there are no
packets to process. Applications should be prepared for this to hap‐
pen, but must not rely on it happening.
(In older versions of libpcap, the behavior when cnt was 0 was unde‐
fined; different platforms and devices behaved differently, so code
that must work with older versions of libpcap should use -1, not 0, as
the value of cnt.)
callback specifies a pcap_handler routine to be called with three argu‐
ments: a u_char pointer which is passed in the user argument to
pcap_loop() or pcap_dispatch(), a const struct pcap_pkthdr pointer
pointing to the packet time stamp and lengths, and a const u_char
pointer to the first caplen (as given in the struct pcap_pkthdr a
pointer to which is passed to the callback routine) bytes of data from
the packet. The struct pcap_pkthdr and the packet data are not to be
freed by the callback routine, and are not guaranteed to be valid after
the callback routine returns; if the code needs them to be valid after
the callback, it must make a copy of them.
The bytes of data from the packet begin with a link-layer header. The
format of the link-layer header is indicated by the return value of the
pcap_datalink(3PCAP) routine when handed the pcap_t value also passed
to pcap_loop() or pcap_dispatch(). https://www.tcpdump.org/link‐
types.html lists the values pcap_datalink() can return and describes
the packet formats that correspond to those values. The value it
returns will be valid for all packets received unless and until
pcap_set_datalink(3PCAP) is called; after a successful call to
pcap_set_datalink(), all subsequent packets will have a link-layer
header of the type specified by the link-layer header type value passed
to pcap_set_datalink().
Do NOT assume that the packets for a given capture or ``savefile`` will
have any given link-layer header type, such as DLT_EN10MB for Ethernet.
For example, the "any" device on Linux will have a link-layer header
type of DLT_LINUX_SLL even if all devices on the system at the time the
"any" device is opened have some other data link type, such as
DLT_EN10MB for Ethernet.
RETURN VALUE
pcap_loop() returns 0 if cnt is exhausted or if, when reading from a
``savefile'', no more packets are available. It returns PCAP_ERROR if
an error occurs or PCAP_ERROR_BREAK if the loop terminated due to a
call to pcap_breakloop() before any packets were processed. It does
not return when live packet buffer timeouts occur; instead, it attempts
to read more packets.
pcap_dispatch() returns the number of packets processed on success;
this can be 0 if no packets were read from a live capture (if, for
example, they were discarded because they didn't pass the packet fil‐
ter, or if, on platforms that support a packet buffer timeout that
starts before any packets arrive, the timeout expires before any pack‐
ets arrive, or if the file descriptor for the capture device is in non-
blocking mode and no packets were available to be read) or if no more
packets are available in a ``savefile.'' It returns PCAP_ERROR if an
error occurs or PCAP_ERROR_BREAK if the loop terminated due to a call
to pcap_breakloop() before any packets were processed. If your appli‐
cation uses pcap_breakloop(), make sure that you explicitly check for
PCAP_ERROR and PCAP_ERROR_BREAK, rather than just checking for a return
value < 0.
If PCAP_ERROR is returned, pcap_geterr(3PCAP) or pcap_perror(3PCAP) may
be called with p as an argument to fetch or display the error text.
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
box; cbp-1 | cbp-1 l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE = Availabil‐
ity system/library/libpcap = Stability Uncommitted
SEE ALSO
pcap(3PCAP)
NOTES
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from https://www.tcpdump.org/release/libp‐
cap-1.9.1.tar.gz.
Further information about this software can be found on the open source
community website at https://www.tcpdump.org/.
25 July 2018 PCAP_LOOP(3pcap)