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PCAP_FINDALLDEVS(3)        Library Functions Manual        PCAP_FINDALLDEVS(3)



NAME
       pcap_findalldevs, pcap_freealldevs - get a list of capture devices, and
       free that list

SYNOPSIS
       #include <pcap/pcap.h>

       char errbuf[PCAP_ERRBUF_SIZE];

       int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf);
       void pcap_freealldevs(pcap_if_t *alldevs);

DESCRIPTION
       pcap_findalldevs() constructs a list of network devices that can be
       opened with pcap_create() and pcap_activate() or with pcap_open_live().
       (Note that there may be network devices that cannot be opened by the
       process calling pcap_findalldevs(), because, for example, that process
       does not have sufficient privileges to open them for capturing; if so,
       those devices will not appear on the list.)  If pcap_findalldevs()
       succeeds, the pointer pointed to by alldevsp is set to point to the
       first element of the list, or to NULL if no devices were found (this is
       considered success).  Each element of the list is of type pcap_if_t,
       and has the following members:

              next   if not NULL, a pointer to the next element in the list;
                     NULL for the last element of the list

              name   a pointer to a string giving a name for the device to
                     pass to pcap_open_live()

              description
                     if not NULL, a pointer to a string giving a human-
                     readable description of the device

              addresses
                     a pointer to the first element of a list of network
                     addresses for the device, or NULL if the device has no
                     addresses

              flags  device flags:

                     PCAP_IF_LOOPBACK
                            set if the device is a loopback interface

       Each element of the list of addresses is of type pcap_addr_t, and has
       the following members:

              next   if not NULL, a pointer to the next element in the list;
                     NULL for the last element of the list

              addr   a pointer to a struct sockaddr containing an address

              netmask
                     if not NULL, a pointer to a struct sockaddr that contains
                     the netmask corresponding to the address pointed to by
                     addr

              broadaddr
                     if not NULL, a pointer to a struct sockaddr that contains
                     the broadcast address corresponding to the address
                     pointed to by addr; may be null if the device doesn't
                     support broadcasts

              dstaddr
                     if not NULL, a pointer to a struct sockaddr that contains
                     the destination address corresponding to the address
                     pointed to by addr; may be null if the device isn't a
                     point-to-point interface

       Note that the addresses in the list of addresses might be IPv4
       addresses, IPv6 addresses, or some other type of addresses, so you must
       check the sa_family member of the struct sockaddr before interpreting
       the contents of the address; do not assume that the addresses are all
       IPv4 addresses, or even all IPv4 or IPv6 addresses.  IPv4 addresses
       have the value AF_INET, IPv6 addresses have the value AF_INET6 (which
       older operating systems that don't support IPv6 might not define), and
       other addresses have other values.  Whether other addresses are
       returned, and what types they might have is platform-dependent.  For
       IPv4 addresses, the struct sockaddr pointer can be interpreted as if it
       pointed to a struct sockaddr_in; for IPv6 addresses, it can be
       interpreted as if it pointed to a struct sockaddr_in6.

       The list of devices must be freed with pcap_freealldevs(), whch frees
       the list pointed to by alldevs.

RETURN VALUE
       pcap_findalldevs() returns 0 on success and -1 on failure; as
       indicated, finding no devices is considered success, rather than
       failure, so 0 will be returned in that case.  If -1 is returned, errbuf
       is filled in with an appropriate error message.  errbuf is assumed to
       be able to hold at least PCAP_ERRBUF_SIZE chars.

SEE ALSO
       pcap(3), pcap_create(3), pcap_activate(3), pcap_open_live(3)



                                22 August 2010             PCAP_FINDALLDEVS(3)