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20 .TH PCAP_FINDALLDEVS 3PCAP "10 January 2014"
21 .SH NAME
22 pcap_findalldevs, pcap_freealldevs \- get a list of capture devices, and
23 free that list
24 .SH SYNOPSIS
25 .nf
26 .ft B
27 #include <pcap/pcap.h>
28 .ft
29 .LP
30 .nf
31 .ft B
32 char errbuf[PCAP_ERRBUF_SIZE];
33 .ft
34 .LP
35 .ft B
36 int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf);
37 void pcap_freealldevs(pcap_if_t *alldevs);
38 .ft
39 .fi
40 .SH DESCRIPTION
41 .B pcap_findalldevs()
42 constructs a list of network devices that can be opened with
43 .B pcap_create()
44 and
45 .B pcap_activate()
46 or with
47 .BR pcap_open_live() .
48 (Note that there may be network devices that cannot be opened by the
49 process calling
50 .BR pcap_findalldevs() ,
51 because, for example, that process does not have sufficient privileges
52 to open them for capturing; if so, those devices will not appear on the
53 list.)
54 If
55 .B pcap_findalldevs()
56 succeeds, the pointer pointed to by
57 .I alldevsp
58 is set to point to the first element of the list, or to
59 .B NULL
60 if no devices were found (this is considered success).
61 Each element of the list is of type
62 .BR pcap_if_t ,
63 and has the following members:
64 .RS
65 .TP
66 .B next
67 if not
68 .BR NULL ,
69 a pointer to the next element in the list;
70 .B NULL
71 for the last element of the list
72 .TP
73 .B name
74 a pointer to a string giving a name for the device to pass to
75 .B pcap_open_live()
76 .TP
77 .B description
78 if not
79 .BR NULL ,
80 a pointer to a string giving a human-readable description of the device
81 .TP
82 .B addresses
83 a pointer to the first element of a list of network addresses for the
84 device,
85 or
86 .B NULL
87 if the device has no addresses
88 .TP
89 .B flags
90 device flags:
91 .RS
92 .TP
93 .B PCAP_IF_LOOPBACK
94 set if the device is a loopback interface
95 .TP
96 .B PCAP_IF_UP
97 set if the device is up
98 .TP
99 .B PCAP_IF_RUNNING
100 set if the device is running
101 .RE
102 .RE
103 .PP
104 Each element of the list of addresses is of type
105 .BR pcap_addr_t ,
106 and has the following members:
107 .RS
108 .TP
109 .B next
110 if not
111 .BR NULL ,
112 a pointer to the next element in the list;
113 .B NULL
114 for the last element of the list
115 .TP
116 .B addr
117 a pointer to a
118 .B "struct sockaddr"
119 containing an address
120 .TP
121 .B netmask
122 if not
123 .BR NULL ,
124 a pointer to a
125 .B "struct sockaddr"
126 that contains the netmask corresponding to the address pointed to by
127 .B addr
128 .TP
129 .B broadaddr
130 if not
131 .BR NULL ,
132 a pointer to a
133 .B "struct sockaddr"
134 that contains the broadcast address corresponding to the address pointed
135 to by
136 .BR addr ;
137 may be null if the device doesn't support broadcasts
138 .TP
139 .B dstaddr
140 if not
141 .BR NULL ,
142 a pointer to a
143 .B "struct sockaddr"
144 that contains the destination address corresponding to the address pointed
145 to by
146 .BR addr ;
147 may be null if the device isn't a point-to-point interface
148 .RE
149 .PP
150 Note that the addresses in the list of addresses might be IPv4
151 addresses, IPv6 addresses, or some other type of addresses, so you must
152 check the
153 .B sa_family
154 member of the
155 .B "struct sockaddr"
156 before interpreting the contents of the address; do not assume that the
157 addresses are all IPv4 addresses, or even all IPv4 or IPv6 addresses.
158 IPv4 addresses have the value
159 .BR AF_INET ,
160 IPv6 addresses have the value
161 .B AF_INET6
162 (which older operating systems that don't support IPv6 might not
163 define), and other addresses have other values. Whether other addresses
164 are returned, and what types they might have is platform-dependent.
165 For IPv4 addresses, the
166 .B "struct sockaddr"
167 pointer can be interpreted as if it pointed to a
168 .BR "struct sockaddr_in" ;
169 for IPv6 addresses, it can be interpreted as if it pointed to a
170 .BR "struct sockaddr_in6".
171 .PP
172 The list of devices must be freed with
173 .BR pcap_freealldevs() ,
174 which frees the list pointed to by
175 .IR alldevs .
176 .SH RETURN VALUE
177 .B pcap_findalldevs()
178 returns 0 on success and \-1 on failure; as indicated, finding no
179 devices is considered success, rather than failure, so 0 will be
180 returned in that case.
181 If \-1 is returned,
182 .I errbuf
183 is filled in with an appropriate error message.
184 .I errbuf
185 is assumed to be able to hold at least
186 .B PCAP_ERRBUF_SIZE
187 chars.
188 .SH SEE ALSO
189 pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP),
190 pcap_open_live(3PCAP)