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GETIFADDRS(3)         DragonFly Library Functions Manual         GETIFADDRS(3)


getifaddrs - get interface addresses


Standard C Library (libc, -lc)


#include <sys/types.h> #include <sys/socket.h> #include <ifaddrs.h> int getifaddrs(struct ifaddrs **ifap); void freeifaddrs(struct ifaddrs *ifp);


The getifaddrs() function stores a reference to a linked list of the network interfaces on the local machine in the memory referenced by ifap. The list consists of ifaddrs structures, as defined in the include file <ifaddrs.h>. The ifaddrs structure contains at least the following entries: struct ifaddrs *ifa_next; /* Pointer to next struct */ char *ifa_name; /* Interface name */ u_int ifa_flags; /* Interface flags */ struct sockaddr *ifa_addr; /* Interface address */ struct sockaddr *ifa_netmask; /* Interface netmask */ struct sockaddr *ifa_dstaddr; /* P2P interface destination */ void *ifa_data; /* Address specific data */ u_int ifa_addrflags; /* Family specific address flags */ The ifa_next field contains a pointer to the next structure on the list. This field is NULL in last structure on the list. The ifa_name field contains the interface name. The ifa_flags field contains the interface flags, as set by ifconfig(8) utility. The ifa_addr field references either the address of the interface or the link level address of the interface, if one exists, otherwise it is NULL. (The sa_family field of the ifa_addr field should be consulted to determine the format of the ifa_addr address.) The ifa_netmask field references the netmask associated with ifa_addr, if one is set, otherwise it is NULL. The ifa_dstaddr field references the destination address on a P2P interface, if one exists, otherwise it is NULL. The ifa_broadaddr field, which should only be referenced for non-P2P interfaces, references the broadcast address associated with ifa_addr, if one exists, otherwise it is NULL. It is really just another name for ifa_dstaddr. The ifa_addrflags field contains the address flags, which are specific to the address family. The ifa_data field references address family specific data. For AF_LINK addresses it contains a pointer to the struct if_data (as defined in include file <net/if.h>) which contains various interface attributes and statistics. For all other address families, it contains a pointer to the struct ifa_data (as defined in include file <net/if.h>) which contains per-address interface statistics. The data returned by getifaddrs() is dynamically allocated and should be freed using freeifaddrs() when no longer needed.


The getifaddrs() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.


The getifaddrs() may fail and set errno for any of the errors specified for the library routines ioctl(2), socket(2), malloc(3) or sysctl(3).


ioctl(2), socket(2), sysctl(3), networking(4), ifconfig(8)


The getifaddrs implementation first appeared in BSDi BSD/OS. if_addrflags was added in NetBSD 8.0.


If both <net/if.h> and <ifaddrs.h> are being included, <net/if.h> must be included before <ifaddrs.h>. DragonFly 5.7-DEVELOPMENT September 12, 2019 DragonFly 5.7-DEVELOPMENT

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