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/* (C) 2013 John Spencer. released under musl's standard MIT license. */
#undef _GNU_SOURCE
#define _GNU_SOURCE
#include <ifaddrs.h>
#include <stdlib.h>
#include <net/if.h> /* IFNAMSIZ, ifreq, ifconf */
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h> /* inet_pton */
#include <unistd.h>
#include <sys/ioctl.h>
typedef union {
struct sockaddr_in6 v6;
struct sockaddr_in v4;
} soa;
typedef struct ifaddrs_storage {
struct ifaddrs ifa;
soa addr;
soa netmask;
soa dst;
char name[IFNAMSIZ+1];
} stor;
#define next ifa.ifa_next
static stor* list_add(stor** list, stor** head, char* ifname)
{
stor* curr = calloc(1, sizeof(stor));
if(curr) {
strcpy(curr->name, ifname);
curr->ifa.ifa_name = curr->name;
if(*head) (*head)->next = (struct ifaddrs*) curr;
*head = curr;
if(!*list) *list = curr;
}
return curr;
}
void freeifaddrs(struct ifaddrs *ifp)
{
stor *head = (stor *) ifp;
while(head) {
void *p = head;
head = (stor *) head->next;
free(p);
}
}
static void ipv6netmask(unsigned prefix_length, struct sockaddr_in6 *sa)
{
unsigned char* hb = sa->sin6_addr.s6_addr;
unsigned onebytes = prefix_length / 8;
unsigned bits = prefix_length % 8;
unsigned nullbytes = 16 - onebytes;
memset(hb, -1, onebytes);
memset(hb+onebytes, 0, nullbytes);
if(bits) {
unsigned char x = -1;
x <<= 8 - bits;
hb[onebytes] = x;
}
}
static void dealwithipv6(stor **list, stor** head)
{
FILE* f = fopen("/proc/net/if_inet6", "r");
/* 00000000000000000000000000000001 01 80 10 80 lo
A B C D E F
all numbers in hex
A = addr B=netlink device#, C=prefix length,
D = scope value (ipv6.h) E = interface flags (rnetlink.h, addrconf.c)
F = if name */
char v6conv[32 + 7 + 1], *v6;
char *line, linebuf[512];
if(!f) return;
while((line = fgets(linebuf, sizeof linebuf, f))) {
v6 = v6conv;
size_t i = 0;
for(; i < 8; i++) {
memcpy(v6, line, 4);
v6+=4;
*v6++=':';
line+=4;
}
--v6; *v6 = 0;
line++;
unsigned b, c, d, e;
char name[IFNAMSIZ+1];
if(5 == sscanf(line, "%x %x %x %x %s", &b, &c, &d, &e, name)) {
struct sockaddr_in6 sa = {0};
if(1 == inet_pton(AF_INET6, v6conv, &sa.sin6_addr)) {
sa.sin6_family = AF_INET6;
stor* curr = list_add(list, head, name);
if(!curr) goto out;
curr->addr.v6 = sa;
curr->ifa.ifa_addr = (struct sockaddr*) &curr->addr;
ipv6netmask(c, &sa);
curr->netmask.v6 = sa;
curr->ifa.ifa_netmask = (struct sockaddr*) &curr->netmask;
/* find ipv4 struct with the same interface name to copy flags */
stor* scan = *list;
for(;scan && strcmp(name, scan->name);scan=(stor*)scan->next);
if(scan) curr->ifa.ifa_flags = scan->ifa.ifa_flags;
else curr->ifa.ifa_flags = 0;
} else errno = 0;
}
}
out:
fclose(f);
}
int getifaddrs(struct ifaddrs **ifap)
{
stor *list = 0, *head = 0;
struct if_nameindex* ii = if_nameindex();
if(!ii) return -1;
size_t i;
for(i = 0; ii[i].if_index || ii[i].if_name; i++) {
stor* curr = list_add(&list, &head, ii[i].if_name);
if(!curr) {
if_freenameindex(ii);
goto err2;
}
}
if_freenameindex(ii);
int sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
if(sock == -1) goto err2;
struct ifreq reqs[32]; /* arbitrary chosen boundary */
struct ifconf conf = {.ifc_len = sizeof reqs, .ifc_req = reqs};
if(-1 == ioctl(sock, SIOCGIFCONF, &conf)) goto err;
size_t reqitems = conf.ifc_len / sizeof(struct ifreq);
for(head = list; head; head = (stor*)head->next) {
for(i = 0; i < reqitems; i++) {
// get SIOCGIFADDR of active interfaces.
if(!strcmp(reqs[i].ifr_name, head->name)) {
head->addr.v4 = *(struct sockaddr_in*)&reqs[i].ifr_addr;
head->ifa.ifa_addr = (struct sockaddr*) &head->addr;
break;
}
}
struct ifreq req;
snprintf(req.ifr_name, sizeof req.ifr_name, "%s", head->name);
if(-1 == ioctl(sock, SIOCGIFFLAGS, &req)) goto err;
head->ifa.ifa_flags = req.ifr_flags;
if(head->ifa.ifa_addr) {
/* or'ing flags with IFF_LOWER_UP on active interfaces to mimic glibc */
head->ifa.ifa_flags |= IFF_LOWER_UP;
if(-1 == ioctl(sock, SIOCGIFNETMASK, &req)) goto err;
head->netmask.v4 = *(struct sockaddr_in*)&req.ifr_netmask;
head->ifa.ifa_netmask = (struct sockaddr*) &head->netmask;
if(head->ifa.ifa_flags & IFF_POINTOPOINT) {
if(-1 == ioctl(sock, SIOCGIFDSTADDR, &req)) goto err;
head->dst.v4 = *(struct sockaddr_in*)&req.ifr_dstaddr;
} else {
if(-1 == ioctl(sock, SIOCGIFBRDADDR, &req)) goto err;
head->dst.v4 = *(struct sockaddr_in*)&req.ifr_broadaddr;
}
head->ifa.ifa_ifu.ifu_dstaddr = (struct sockaddr*) &head->dst;
}
}
close(sock);
void* last = 0;
for(head = list; head; head=(stor*)head->next) last=head;
head = last;
dealwithipv6(&list, &head);
*ifap = (struct ifaddrs*) list;
return 0;
err:
close(sock);
err2:
freeifaddrs((struct ifaddrs*) list);
return -1;
}
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