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22 .TH PCAP_FINDALLDEVS 3PCAP "10 January 2014"
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 .TP
98 .B PCAP_IF_UP
99 set if the device is up
100 .TP
101 .B PCAP_IF_RUNNING
102 set if the device is running
103 .RE
104 .RE
105 .PP
106 Each element of the list of addresses is of type
107 .BR pcap_addr_t ,
108 and has the following members:
109 .RS
110 .TP
111 .B next
112 if not
113 .BR NULL ,
114 a pointer to the next element in the list;
115 .B NULL
116 for the last element of the list
117 .TP
118 .B addr
119 a pointer to a
120 .B "struct sockaddr"
121 containing an address
122 .TP
123 .B netmask
124 if not
125 .BR NULL ,
126 a pointer to a
127 .B "struct sockaddr"
128 that contains the netmask corresponding to the address pointed to by
129 .B addr
130 .TP
131 .B broadaddr
132 if not
133 .BR NULL ,
134 a pointer to a
135 .B "struct sockaddr"
136 that contains the broadcast address corresponding to the address pointed
137 to by
138 .BR addr ;
139 may be null if the device doesn't support broadcasts
140 .TP
141 .B dstaddr
142 if not
143 .BR NULL ,
144 a pointer to a
145 .B "struct sockaddr"
146 that contains the destination address corresponding to the address pointed
147 to by
148 .BR addr ;
149 may be null if the device isn't a point-to-point interface
150 .RE
151 .PP
152 Note that the addresses in the list of addresses might be IPv4
153 addresses, IPv6 addresses, or some other type of addresses, so you must
154 check the
155 .B sa_family
156 member of the
157 .B "struct sockaddr"
158 before interpreting the contents of the address; do not assume that the
159 addresses are all IPv4 addresses, or even all IPv4 or IPv6 addresses.
160 IPv4 addresses have the value
161 .BR AF_INET ,
162 IPv6 addresses have the value
163 .B AF_INET6
164 (which older operating systems that don't support IPv6 might not
165 define), and other addresses have other values. Whether other addresses
166 are returned, and what types they might have is platform-dependent.
167 For IPv4 addresses, the
168 .B "struct sockaddr"
169 pointer can be interpreted as if it pointed to a
170 .BR "struct sockaddr_in" ;
171 for IPv6 addresses, it can be interpreted as if it pointed to a
172 .BR "struct sockaddr_in6".
173 .PP
174 The list of devices must be freed with
175 .BR pcap_freealldevs() ,
176 which frees the list pointed to by
177 .IR alldevs .
178 .SH RETURN VALUE
179 .B pcap_findalldevs()
180 returns 0 on success and \-1 on failure; as indicated, finding no
181 devices is considered success, rather than failure, so 0 will be
182 returned in that case.
183 If \-1 is returned,
184 .I errbuf
185 is filled in with an appropriate error message.
186 .I errbuf
187 is assumed to be able to hold at least
188 .B PCAP_ERRBUF_SIZE
189 chars.
190 .SH SEE ALSO
191 pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP),
192 pcap_open_live(3PCAP)