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pcap_next_ex(3pcap)

PCAP_NEXT_EX(3pcap)                                        PCAP_NEXT_EX(3pcap)

NAME
       pcap_next_ex, pcap_next - read the next packet from a pcap_t

SYNOPSIS
       #include <pcap/pcap.h>

       int pcap_next_ex(pcap_t *p, struct pcap_pkthdr **pkt_header,
               const u_char **pkt_data);
       const u_char *pcap_next(pcap_t *p, struct pcap_pkthdr *h);

DESCRIPTION
       pcap_next_ex()  reads the next packet and returns a success/failure in‐
       dication.  If the packet was read without problems, the pointer pointed
       to by the pkt_header argument is set to point to the pcap_pkthdr struct
       for the packet, and the pointer pointed to by the pkt_data argument  is
       set to point to the data in the packet.  The struct pcap_pkthdr and the
       packet  data  are not to be freed by the caller, and are not guaranteed
       to be  valid  after  the  next  call  to  pcap_next_ex(),  pcap_next(),
       pcap_loop(3PCAP),  or  pcap_dispatch(3PCAP);  if the code needs them to
       remain valid, it must make a copy of them.

       pcap_next() reads the next packet (by calling  pcap_dispatch()  with  a
       cnt of 1) and returns a u_char pointer to the data in that packet.  The
       packet  data is not to be freed by the caller, and is not guaranteed to
       be  valid  after  the  next  call   to   pcap_next_ex(),   pcap_next(),
       pcap_loop(),  or pcap_dispatch(); if the code needs it to remain valid,
       it must make a copy of it.  The pcap_pkthdr structure pointed to  by  h
       is filled in with the appropriate values for the packet.

       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 re‐
       turns  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 or DLT_LINUX_SLL2 even if all devices on the sys‐
       tem at the time the "any" device is opened have some  other  data  link
       type, such as DLT_EN10MB for Ethernet.

RETURN VALUE
       pcap_next_ex()  returns 1 if the packet was read without problems, 0 if
       packets are being read from a live capture and the packet buffer  time‐
       out  expired, PCAP_ERROR_BREAK if packets are being read from a ``save‐
       file'' and there are  no  more  packets  to  read  from  the  savefile,
       PCAP_ERROR_NOT_ACTIVATED  if  called  on a capture handle that has been
       created but not activated, or PCAP_ERROR if  an  error  occurred  while
       reading  the  packet.  If PCAP_ERROR is returned, pcap_geterr(3PCAP) or
       pcap_perror(3PCAP) may be called with p as an argument to fetch or dis‐
       play the error text.

       pcap_next() returns a pointer to the packet data on  success,  and  re‐
       turns NULL if an error occurred, or if no packets were read from a live
       capture  (if, for example, they were discarded because they didn't pass
       the packet filter, or if, on platforms that  support  a  packet  buffer
       timeout  that starts before any packets arrive, the timeout expires be‐
       fore any packets arrive, or if the file descriptor for the capture  de‐
       vice is in non-blocking mode and no packets were available to be read),
       or  if  no more packets are available in a ``savefile.'' Unfortunately,
       there is no way to determine whether an error occurred or not.


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/libpcap-1.10.4.tar.gz

       Further information about this software can be found on the open source
       community website at https://www.tcpdump.org/.

                                 5 March 2022              PCAP_NEXT_EX(3pcap)
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