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 indication.  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(), or pcap_dispatch(); 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()  routine  when  handed  the  pcap_t value also passed to pcap_loop() or pcap_dispatch().  http://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()  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 Eth-
       ernet.  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_next_ex()  returns 1 if the packet was read without problems, 0 if packets are being read from a live capture and the timeout expired,
       -1 if an error occurred while reading the packet, and -2 if packets are being read from a ``savefile'' and there are  no  more  packets	to
       read  from  the	savefile.   If	-1 is returned, pcap_geterr() or pcap_perror() may be called with p as an argument to fetch or display the
       error text.

       pcap_next() returns a pointer to the packet data on success, and returns 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 read timeout
       that starts before any packets arrive, the timeout expires before any packets 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.''  Unfortunately,
       there is no way to determine whether an error occurred or not.

SEE ALSO

       pcap(3PCAP), pcap_geterr(3PCAP), pcap_dispatch(3PCAP), pcap_datalink(3PCAP)

								   7 April 2014 					       PCAP_NEXT_EX(3PCAP)