1 /* (C) 2013 John Spencer. released under musl's standard MIT license. */
6 #include <net/if.h> /* IFNAMSIZ, ifreq, ifconf */
11 #include <arpa/inet.h> /* inet_pton */
13 #include <sys/ioctl.h>
16 struct sockaddr_in6 v6;
17 struct sockaddr_in v4;
20 typedef struct ifaddrs_storage {
25 char name[IFNAMSIZ+1];
27 #define next ifa.ifa_next
29 static stor* list_add(stor** list, stor** head, char* ifname)
31 stor* curr = calloc(1, sizeof(stor));
33 strcpy(curr->name, ifname);
34 curr->ifa.ifa_name = curr->name;
35 if(*head) (*head)->next = (struct ifaddrs*) curr;
37 if(!*list) *list = curr;
42 void freeifaddrs(struct ifaddrs *ifp)
44 stor *head = (stor *) ifp;
47 head = (stor *) head->next;
52 static void ipv6netmask(unsigned prefix_length, struct sockaddr_in6 *sa)
54 unsigned char* hb = sa->sin6_addr.s6_addr;
55 unsigned onebytes = prefix_length / 8;
56 unsigned bits = prefix_length % 8;
57 unsigned nullbytes = 16 - onebytes;
58 memset(hb, -1, onebytes);
59 memset(hb+onebytes, 0, nullbytes);
67 static void dealwithipv6(stor **list, stor** head)
69 FILE* f = fopen("/proc/net/if_inet6", "r");
70 /* 00000000000000000000000000000001 01 80 10 80 lo
73 A = addr B=netlink device#, C=prefix length,
74 D = scope value (ipv6.h) E = interface flags (rnetlink.h, addrconf.c)
76 char v6conv[32 + 7 + 1], *v6;
77 char *line, linebuf[512];
79 while((line = fgets(linebuf, sizeof linebuf, f))) {
91 char name[IFNAMSIZ+1];
92 if(5 == sscanf(line, "%x %x %x %x %s", &b, &c, &d, &e, name)) {
93 struct sockaddr_in6 sa = {0};
94 if(1 == inet_pton(AF_INET6, v6conv, &sa.sin6_addr)) {
95 sa.sin6_family = AF_INET6;
96 stor* curr = list_add(list, head, name);
99 curr->ifa.ifa_addr = (struct sockaddr*) &curr->addr;
101 curr->netmask.v6 = sa;
102 curr->ifa.ifa_netmask = (struct sockaddr*) &curr->netmask;
103 /* find ipv4 struct with the same interface name to copy flags */
105 for(;scan && strcmp(name, scan->name);scan=(stor*)scan->next);
106 if(scan) curr->ifa.ifa_flags = scan->ifa.ifa_flags;
107 else curr->ifa.ifa_flags = 0;
115 int getifaddrs(struct ifaddrs **ifap)
117 stor *list = 0, *head = 0;
118 struct if_nameindex* ii = if_nameindex();
121 for(i = 0; ii[i].if_index || ii[i].if_name; i++) {
122 stor* curr = list_add(&list, &head, ii[i].if_name);
124 if_freenameindex(ii);
128 if_freenameindex(ii);
130 int sock = socket(PF_INET, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_IP);
131 if(sock == -1) goto err2;
132 struct ifreq reqs[32]; /* arbitrary chosen boundary */
133 struct ifconf conf = {.ifc_len = sizeof reqs, .ifc_req = reqs};
134 if(-1 == ioctl(sock, SIOCGIFCONF, &conf)) goto err;
135 size_t reqitems = conf.ifc_len / sizeof(struct ifreq);
136 for(head = list; head; head = (stor*)head->next) {
137 for(i = 0; i < reqitems; i++) {
138 // get SIOCGIFADDR of active interfaces.
139 if(!strcmp(reqs[i].ifr_name, head->name)) {
140 head->addr.v4 = *(struct sockaddr_in*)&reqs[i].ifr_addr;
141 head->ifa.ifa_addr = (struct sockaddr*) &head->addr;
146 snprintf(req.ifr_name, sizeof req.ifr_name, "%s", head->name);
147 if(-1 == ioctl(sock, SIOCGIFFLAGS, &req)) goto err;
149 head->ifa.ifa_flags = req.ifr_flags;
150 if(head->ifa.ifa_addr) {
151 /* or'ing flags with IFF_LOWER_UP on active interfaces to mimic glibc */
152 head->ifa.ifa_flags |= IFF_LOWER_UP;
153 if(-1 == ioctl(sock, SIOCGIFNETMASK, &req)) goto err;
154 head->netmask.v4 = *(struct sockaddr_in*)&req.ifr_netmask;
155 head->ifa.ifa_netmask = (struct sockaddr*) &head->netmask;
157 if(head->ifa.ifa_flags & IFF_POINTOPOINT) {
158 if(-1 == ioctl(sock, SIOCGIFDSTADDR, &req)) goto err;
159 head->dst.v4 = *(struct sockaddr_in*)&req.ifr_dstaddr;
161 if(-1 == ioctl(sock, SIOCGIFBRDADDR, &req)) goto err;
162 head->dst.v4 = *(struct sockaddr_in*)&req.ifr_broadaddr;
164 head->ifa.ifa_ifu.ifu_dstaddr = (struct sockaddr*) &head->dst;
169 for(head = list; head; head=(stor*)head->next) last=head;
171 dealwithipv6(&list, &head);
172 *ifap = (struct ifaddrs*) list;
177 freeifaddrs((struct ifaddrs*) list);