Get information on network interfaces in FreeBSD
This C code gives information on network interfaces, including the IP address and the MAC address of the interfaces, on FreeBSD.
#include <stdio.h> #include <stdlib.h> /* The following include files for the network interface. */ #include <sys/types.h> #include <sys/socket.h> #include <ifaddrs.h> #include <net/if.h> #include <net/if_dl.h> #include <netinet/in.h> #include <arpa/inet.h> #include <net/if_types.h> /* For "toupper". */ #include <ctype.h> /* For "strerror". */ #include <string.h> /* For "errno". */ #include <errno.h> /* Print an internet address. */ void print_ip (const char * name, struct ifaddrs * ifaddrs_ptr, void * addr_ptr) { if (addr_ptr) { /* This constant is defined in <netinet/in.h>. */ char address[INET6_ADDRSTRLEN]; inet_ntop (ifaddrs_ptr->ifa_addr->sa_family, addr_ptr, address, sizeof (address)); /* The "toupper" capitalizes the first letter. */ printf ("%c%s: <%s>\n", toupper (name[0]), name + 1, address); } else { printf ("No %s\n", name); } } /* Get a pointer to the address structure from a sockaddr. */ void * get_addr_ptr (struct sockaddr * sockaddr_ptr) { void * addr_ptr = 0; if (sockaddr_ptr->sa_family == AF_INET) { addr_ptr = &((struct sockaddr_in *) sockaddr_ptr)->sin_addr; } else if (sockaddr_ptr->sa_family == AF_INET6) { addr_ptr = &((struct sockaddr_in6 *) sockaddr_ptr)->sin6_addr; } return addr_ptr; } /* Print the internet address. */ void print_internet_address (struct ifaddrs * ifaddrs_ptr) { void * addr_ptr; if (! ifaddrs_ptr->ifa_addr) { return; } addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_addr); print_ip ("internet address", ifaddrs_ptr, addr_ptr); } /* Print the netmask. */ void print_netmask (struct ifaddrs * ifaddrs_ptr) { void * addr_ptr; if (! ifaddrs_ptr->ifa_netmask) { return; } addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_netmask); print_ip ("netmask", ifaddrs_ptr, addr_ptr); } /* Print the mac address. */ void print_mac_address (const char * mac_address) { int mac_addr_offset; printf ("Mac address: "); for (mac_addr_offset = 0; mac_addr_offset < 6; mac_addr_offset++) { unsigned char byte; byte = (unsigned char) mac_address[mac_addr_offset]; printf ("%02x", byte); if (mac_addr_offset != 5) { printf (":"); } } printf ("\n"); } /* Adapted from http://othermark.livejournal.com/3005.html */ void print_af_link (struct ifaddrs * ifaddrs_ptr) { struct sockaddr_dl * sdl; sdl = (struct sockaddr_dl *) ifaddrs_ptr->ifa_addr; /* The types "IFT_ETHER" and so on are defined in <net/if_types.h>. */ if (sdl->sdl_type == IFT_ETHER) { print_mac_address (LLADDR (sdl)); } else if (sdl->sdl_type == IFT_LOOP) { printf ("Loopback.\n"); } else if (sdl->sdl_type == IFT_USB) { printf ("USB interface.\n"); } else { printf ("Link of type %d\n", sdl->sdl_type); } } void print_internet_interface (struct ifaddrs * ifaddrs_ptr) { print_internet_address (ifaddrs_ptr); print_netmask (ifaddrs_ptr); /* P2P interface destination */ if (ifaddrs_ptr->ifa_dstaddr) { void * addr_ptr; addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_dstaddr); print_ip ("destination address", ifaddrs_ptr, addr_ptr); } /* Interface broadcast address */ if (ifaddrs_ptr->ifa_broadaddr) { void * addr_ptr; addr_ptr = get_addr_ptr (ifaddrs_ptr->ifa_broadaddr); print_ip ("broadcast address", ifaddrs_ptr, addr_ptr); } } /* Adapted from http://publib.boulder.ibm.com/infocenter/iseries/v6r1m0/index.jsp?topic=/apis/getifaddrs.htm */ void print_ifaddrs (struct ifaddrs * ifaddrs_ptr) { while (ifaddrs_ptr) { printf ("Name: %s; Flags: 0x%x; ", ifaddrs_ptr->ifa_name, ifaddrs_ptr->ifa_flags); /* Decide what to do based on the family. */ if (ifaddrs_ptr->ifa_addr->sa_family == AF_INET) { /* AF_INET is defined in <sys/socket.h>. */ printf ("Family: AF_INET\n"); print_internet_interface (ifaddrs_ptr); } else if (ifaddrs_ptr->ifa_addr->sa_family == AF_INET6) { printf ("Family: AF_INET6\n"); print_internet_interface (ifaddrs_ptr); } else if (ifaddrs_ptr->ifa_addr->sa_family == AF_LINK) { printf ("Family: AF_LINK\n"); print_af_link (ifaddrs_ptr); } else { printf ("Unknown family"); } /* Print a line between this entry and the next. */ printf ("\n"); ifaddrs_ptr = ifaddrs_ptr->ifa_next; } } int main () { struct ifaddrs * ifaddrs_ptr; int status; status = getifaddrs (& ifaddrs_ptr); if (status == -1) { fprintf (stderr, "Error in 'getifaddrs': %d (%s)\n", errno, strerror (errno)); exit (1); } print_ifaddrs (ifaddrs_ptr); /* Free the memory associated with "ifaddrs_ptr". */ freeifaddrs (ifaddrs_ptr); return 0; }
Web links
-
ifnet, ifaddr, ifqueue, if_data – kernel interfaces for manipulating network interfaces
Online manual page.
- IFT_ assignments
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