1GETIFADDRS(3) Linux Programmer's Manual GETIFADDRS(3)
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6 getifaddrs, freeifaddrs - get interface addresses
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9 #include <sys/types.h>
10 #include <ifaddrs.h>
11 int getifaddrs(struct ifaddrs **ifap);
13 void freeifaddrs(struct ifaddrs *ifa);
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17 The getifaddrs() function creates a linked list of structures describ‐
18 ing the network interfaces of the local system, and stores the address
19 of the first item of the list in *ifap. The list consists of ifaddrs
20 structures, defined as follows:
21 struct ifaddrs {
23 struct ifaddrs *ifa_next; /* Next item in list */
24 char *ifa_name; /* Name of interface */
25 unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */
26 struct sockaddr *ifa_addr; /* Address of interface */
27 struct sockaddr *ifa_netmask; /* Netmask of interface */
28 union {
29 struct sockaddr *ifu_broadaddr;
30 /* Broadcast address of interface */
31 struct sockaddr *ifu_dstaddr;
32 /* Point-to-point destination address */
33 } ifa_ifu;
34 #define ifa_broadaddr ifa_ifu.ifu_broadaddr
35 #define ifa_dstaddr ifa_ifu.ifu_dstaddr
36 void *ifa_data; /* Address-specific data */
37 };
38 The ifa_next field contains a pointer to the next structure on the
40 list, or NULL if this is the last item of the list.
41 The ifa_name points to the null-terminated interface name.
43 The ifa_flags field contains the interface flags, as returned by the
45 SIOCGIFFLAGS ioctl(2) operation (see netdevice(7) for a list of these
46 flags).
47 The ifa_addr field points to a structure containing the interface
49 address. (The sa_family subfield should be consulted to determine the
50 format of the address structure.) This field may contain a null
51 pointer.
52 The ifa_netmask field points to a structure containing the netmask
54 associated with ifa_addr, if applicable for the address family. This
55 field may contain a null pointer.
56 Depending on whether the bit IFF_BROADCAST or IFF_POINTOPOINT is set in
58 ifa_flags (only one can be set at a time), either ifa_broadaddr will
59 contain the broadcast address associated with ifa_addr (if applicable
60 for the address family) or ifa_dstaddr will contain the destination
61 address of the point-to-point interface.
62 The ifa_data field points to a buffer containing address-family-spe‐
64 cific data; this field may be NULL if there is no such data for this
65 interface.
66 The data returned by getifaddrs() is dynamically allocated and should
68 be freed using freeifaddrs() when no longer needed.
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71 On success, getifaddrs() returns zero; on error, -1 is returned, and
72 errno is set appropriately.
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75 getifaddrs() may fail and set errno for any of the errors specified for
76 socket(2), bind(2), getsockname(2), recvmsg(2), sendto(2),