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  20 .TH PCAP_SET_PROTOCOL 3PCAP "3 January 2014"
  21 .SH NAME
  22 pcap_set_protocol \- set capture protocol for a not-yet-activated
  23 capture handle
  24 .SH SYNOPSIS
  25 .nf
  26 .ft B
  27 #include <pcap/pcap.h>
  28 .LP
  29 .ft B
  30 int pcap_set_protocol(pcap_t *p, int protocol);
  31 .ft
  32 .fi
  33 .SH DESCRIPTION
  34 .B pcap_set_protocol()
  35 sets the protocol to be used in the
  36 .BR socket (2)
  37 call to create a capture socket when the handle is activated.  The
  38 argument is a link-layer protocol value, such as the values in the
  39 .B <linux/if_ether.h>
  40 header file, specified in host byte order.
  41 If
  42 .I protocol
  43 is non-zero, packets of that protocol will be captured when the
  44 handle is activated, otherwise, all packets will be captured.  This
  45 function is only provided on Linux, and, if it is used on any device
  46 other than a network interface, it will have no effect.
  47 .SH RETURN VALUE
  48 .B pcap_set_protocol()
  49 returns 0 on success or
  50 .B PCAP_ERROR_ACTIVATED
  51 if called on a capture handle that has been activated.
  52 .SH SEE ALSO
  53 pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP)