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  22 .TH PCAP_FINDALLDEVS 3PCAP "22 August 2010"
  23 .SH NAME
  24 pcap_findalldevs, pcap_freealldevs \- get a list of capture devices, and
  25 free that list
  26 .SH SYNOPSIS
  27 .nf
  28 .ft B
  29 #include <pcap/pcap.h>
  30 .ft
  31 .LP
  32 .nf
  33 .ft B
  34 char errbuf[PCAP_ERRBUF_SIZE];
  35 .ft
  36 .LP
  37 .ft B
  38 int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf);
  39 void pcap_freealldevs(pcap_if_t *alldevs);
  40 .ft
  41 .fi
  42 .SH DESCRIPTION
  43 .B pcap_findalldevs()
  44 constructs a list of network devices that can be opened with
  45 .B pcap_create()
  46 and
  47 .B pcap_activate()
  48 or with
  49 .BR pcap_open_live() .
  50 (Note that there may be network devices that cannot be opened by the
  51 process calling
  52 .BR pcap_findalldevs() ,
  53 because, for example, that process does not have sufficient privileges
  54 to open them for capturing; if so, those devices will not appear on the
  55 list.)
  56 If
  57 .B pcap_findalldevs()
  58 succeeds, the pointer pointed to by
  59 .I alldevsp
  60 is set to point to the first element of the list, or to
  61 .B NULL
  62 if no devices were found (this is considered success).
  63 Each element of the list is of type
  64 .BR pcap_if_t ,
  65 and has the following members:
  66 .RS
  67 .TP
  68 .B next
  69 if not
  70 .BR NULL ,
  71 a pointer to the next element in the list;
  72 .B NULL
  73 for the last element of the list
  74 .TP
  75 .B name
  76 a pointer to a string giving a name for the device to pass to
  77 .B pcap_open_live()
  78 .TP
  79 .B description
  80 if not
  81 .BR NULL ,
  82 a pointer to a string giving a human-readable description of the device
  83 .TP
  84 .B addresses
  85 a pointer to the first element of a list of network addresses for the
  86 device,
  87 or
  88 .B NULL
  89 if the device has no addresses
  90 .TP
  91 .B flags
  92 device flags:
  93 .RS
  94 .TP
  95 .B PCAP_IF_LOOPBACK
  96 set if the device is a loopback interface
  97 .RE
  98 .RE
  99 .PP
 100 Each element of the list of addresses is of type
 101 .BR pcap_addr_t ,
 102 and has the following members:
 103 .RS
 104 .TP
 105 .B next
 106 if not
 107 .BR NULL ,
 108 a pointer to the next element in the list;
 109 .B NULL
 110 for the last element of the list
 111 .TP
 112 .B addr
 113 a pointer to a
 114 .B "struct sockaddr"
 115 containing an address
 116 .TP
 117 .B netmask
 118 if not
 119 .BR NULL ,
 120 a pointer to a
 121 .B "struct sockaddr"
 122 that contains the netmask corresponding to the address pointed to by
 123 .B addr
 124 .TP
 125 .B broadaddr
 126 if not
 127 .BR NULL ,
 128 a pointer to a
 129 .B "struct sockaddr"
 130 that contains the broadcast address corresponding to the address pointed
 131 to by
 132 .BR addr ;
 133 may be null if the device doesn't support broadcasts
 134 .TP
 135 .B dstaddr
 136 if not
 137 .BR NULL ,
 138 a pointer to a
 139 .B "struct sockaddr"
 140 that contains the destination address corresponding to the address pointed
 141 to by
 142 .BR addr ;
 143 may be null if the device isn't a point-to-point interface
 144 .RE
 145 .PP
 146 Note that not all the addresses in the list of addresses are
 147 necessarily IPv4 or IPv6 addresses - you must check the
 148 .B sa_family
 149 member of the
 150 .B "struct sockaddr"
 151 before interpreting the contents of the address.
 152 .PP
 153 The list of devices must be freed with
 154 .BR pcap_freealldevs() ,
 155 whch frees the list pointed to by
 156 .IR alldevs .
 157 .SH RETURN VALUE
 158 .B pcap_findalldevs()
 159 returns 0 on success and \-1 on failure; as indicated, finding no
 160 devices is considered success, rather than failure, so 0 will be
 161 returned in that case.
 162 If \-1 is returned,
 163 .I errbuf
 164 is filled in with an appropriate error message.
 165 .I errbuf
 166 is assumed to be able to hold at least
 167 .B PCAP_ERRBUF_SIZE
 168 chars.
 169 .SH SEE ALSO
 170 pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP),
 171 pcap_open_live(3PCAP)