reimplement if_nameindex and getifaddrs using netlink

the previous implementations had several deficiencies, the most severe
of which was the inability to report unconfigured interfaces or
interfaces without ipv4 addresses. among the options discussed for
fixing this, using netlink turned out to be the one with the least
cost and most additional advantages. other improvements include:

if_nameindex now avoids duplicates in the list it produces, but still
includes legacy-style interface aliases if any are in use.

getifaddrs now reports hardware addresses and includes the scope_id
for link-local ipv6 addresses in the resulting address.

1 files changed, 168 insertions, 146 deletions

diff --git a/src/network/getifaddrs.c b/src/network/getifaddrs.c
index 5a94cc7c..89a8f729 100644
--- a/src/network/getifaddrs.c
+++ b/src/network/getifaddrs.c
@@ -1,181 +1,203 @@
-/* (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 <string.h>
+#include <stdlib.h>
 #include <unistd.h>
-#include <sys/ioctl.h>
-#include <sys/socket.h>
+#include <ifaddrs.h>
+#include <syscall.h>
+#include <net/if.h>
+#include <netinet/in.h>
+#include "netlink.h"
 
-typedef union {
-	struct sockaddr_in6 v6;
+#define IFADDRS_HASH_SIZE 64
+
+/* getifaddrs() reports hardware addresses with PF_PACKET that implies
+ * struct sockaddr_ll.  But e.g. Infiniband socket address length is
+ * longer than sockaddr_ll.ssl_addr[8] can hold. Use this hack struct
+ * to extend ssl_addr - callers should be able to still use it. */
+struct sockaddr_ll_hack {
+	unsigned short sll_family, sll_protocol;
+	int sll_ifindex;
+	unsigned short sll_hatype;
+	unsigned char sll_pkttype, sll_halen;
+	unsigned char sll_addr[24];
+};
+
+union sockany {
+	struct sockaddr sa;
+	struct sockaddr_ll_hack ll;
 	struct sockaddr_in v4;
-} soa;
+	struct sockaddr_in6 v6;
+};
 
-typedef struct ifaddrs_storage {
+struct ifaddrs_storage {
 	struct ifaddrs ifa;
-	soa addr;
-	soa netmask;
-	soa dst;
+	struct ifaddrs_storage *hash_next;
+	union sockany addr, netmask, ifu;
+	unsigned int index;
 	char name[IFNAMSIZ+1];
-} stor;
-#define next ifa.ifa_next
+};
 
-static stor* list_add(stor** list, stor** head, char* ifname)
+struct ifaddrs_ctx {
+	struct ifaddrs_storage *first;
+	struct ifaddrs_storage *last;
+	struct ifaddrs_storage *hash[IFADDRS_HASH_SIZE];
+};
+
+void freeifaddrs(struct ifaddrs *ifp)
 {
-	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;
+	struct ifaddrs *n;
+	while (ifp) {
+		n = ifp->ifa_next;
+		free(ifp);
+		ifp = n;
 	}
-	return curr;
 }
 
-void freeifaddrs(struct ifaddrs *ifp)
+static void copy_addr(struct sockaddr **r, int af, union sockany *sa, void *addr, size_t addrlen, int ifindex)
 {
-	stor *head = (stor *) ifp;
-	while(head) {
-		void *p = head;
-		head = (stor *) head->next;
-		free(p);
+	uint8_t *dst;
+	int len;
+
+	switch (af) {
+	case AF_INET:
+		dst = (uint8_t*) &sa->v4.sin_addr;
+		len = 4;
+		break;
+	case AF_INET6:
+		dst = (uint8_t*) &sa->v6.sin6_addr;
+		len = 16;
+		if (IN6_IS_ADDR_LINKLOCAL(addr) || IN6_IS_ADDR_MC_LINKLOCAL(addr))
+			sa->v6.sin6_scope_id = ifindex;
+		break;
+	default:
+		return;
 	}
+	if (addrlen < len) return;
+	sa->sa.sa_family = af;
+	memcpy(dst, addr, len);
+	*r = &sa->sa;
 }
 
-static void ipv6netmask(unsigned prefix_length, struct sockaddr_in6 *sa)
+static void gen_netmask(struct sockaddr **r, int af, union sockany *sa, int prefixlen)
 {
-	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;
-	}
+	uint8_t addr[16] = {0};
+	int i;
+
+	if (prefixlen > 8*sizeof(addr)) prefixlen = 8*sizeof(addr);
+	i = prefixlen / 8;
+	memset(addr, 0xff, i);
+	if (i < sizeof(addr)) addr[i++] = 0xff << (8 - (prefixlen % 8));
+	copy_addr(r, af, sa, addr, sizeof(addr), 0);
 }
 
-static void dealwithipv6(stor **list, stor** head)
+static void copy_lladdr(struct sockaddr **r, union sockany *sa, void *addr, size_t addrlen, int ifindex, unsigned short hatype)
 {
-	FILE* f = fopen("/proc/net/if_inet6", "rbe");
-	/* 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);
+	if (addrlen > sizeof(sa->ll.sll_addr)) return;
+	sa->ll.sll_family = AF_PACKET;
+	sa->ll.sll_ifindex = ifindex;
+	sa->ll.sll_hatype = hatype;
+	sa->ll.sll_halen = addrlen;
+	memcpy(sa->ll.sll_addr, addr, addrlen);
+	*r = &sa->sa;
 }
 
-int getifaddrs(struct ifaddrs **ifap)
+static int netlink_msg_to_ifaddr(void *pctx, struct nlmsghdr *h)
 {
-	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;
+	struct ifaddrs_ctx *ctx = pctx;
+	struct ifaddrs_storage *ifs, *ifs0;
+	struct ifinfomsg *ifi = NLMSG_DATA(h);
+	struct ifaddrmsg *ifa = NLMSG_DATA(h);
+	struct rtattr *rta;
+	int stats_len = 0;
+
+	if (h->nlmsg_type == RTM_NEWLINK) {
+		for (rta = NLMSG_RTA(h, sizeof(*ifi)); NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
+			if (rta->rta_type != IFLA_STATS) continue;
+			stats_len = RTA_DATALEN(rta);
+			break;
 		}
+	} else {
+		for (ifs0 = ctx->hash[ifa->ifa_index % IFADDRS_HASH_SIZE]; ifs0; ifs0 = ifs0->hash_next)
+			if (ifs0->index == ifa->ifa_index)
+				break;
+		if (!ifs0) return 0;
 	}
-	if_freenameindex(ii);
-
-	int sock = socket(PF_INET, SOCK_DGRAM|SOCK_CLOEXEC, 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;
+
+	ifs = calloc(1, sizeof(struct ifaddrs_storage) + stats_len);
+	if (ifs == 0) return -1;
+
+	if (h->nlmsg_type == RTM_NEWLINK) {
+		ifs->index = ifi->ifi_index;
+		ifs->ifa.ifa_flags = ifi->ifi_flags;
+
+		for (rta = NLMSG_RTA(h, sizeof(*ifi)); NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
+			switch (rta->rta_type) {
+			case IFLA_IFNAME:
+				if (RTA_DATALEN(rta) < sizeof(ifs->name)) {
+					memcpy(ifs->name, RTA_DATA(rta), RTA_DATALEN(rta));
+					ifs->ifa.ifa_name = ifs->name;
+				}
+				break;
+			case IFLA_ADDRESS:
+				copy_lladdr(&ifs->ifa.ifa_addr, &ifs->addr, RTA_DATA(rta), RTA_DATALEN(rta), ifi->ifi_index, ifi->ifi_type);
+				break;
+			case IFLA_BROADCAST:
+				copy_lladdr(&ifs->ifa.ifa_broadaddr, &ifs->ifu, RTA_DATA(rta), RTA_DATALEN(rta), ifi->ifi_index, ifi->ifi_type);
+				break;
+			case IFLA_STATS:
+				ifs->ifa.ifa_data = (void*)(ifs+1);
+				memcpy(ifs->ifa.ifa_data, RTA_DATA(rta), RTA_DATALEN(rta));
 				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;
+		if (ifs->ifa.ifa_name) {
+			unsigned int bucket = ifs->index % IFADDRS_HASH_SIZE;
+			ifs->hash_next = ctx->hash[bucket];
+			ctx->hash[bucket] = ifs;
+		}
+	} else {
+		ifs->ifa.ifa_name = ifs0->ifa.ifa_name;
+		ifs->ifa.ifa_flags = ifs0->ifa.ifa_flags;
+		for (rta = NLMSG_RTA(h, sizeof(*ifa)); NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
+			switch (rta->rta_type) {
+			case IFA_ADDRESS:
+				copy_addr(&ifs->ifa.ifa_addr, ifa->ifa_family, &ifs->addr, RTA_DATA(rta), RTA_DATALEN(rta), ifa->ifa_index);
+				break;
+			case IFA_BROADCAST:
+				/* For point-to-point links this is peer, but ifa_broadaddr
+				 * and ifa_dstaddr are union, so this works for both.  */
+				copy_addr(&ifs->ifa.ifa_broadaddr, ifa->ifa_family, &ifs->ifu, RTA_DATA(rta), RTA_DATALEN(rta), ifa->ifa_index);
+				break;
+			case IFA_LABEL:
+				if (RTA_DATALEN(rta) < sizeof(ifs->name)) {
+					memcpy(ifs->name, RTA_DATA(rta), RTA_DATALEN(rta));
+					ifs->ifa.ifa_name = ifs->name;
+				}
+				break;
 			}
-			head->ifa.ifa_ifu.ifu_dstaddr = (struct sockaddr*) &head->dst;
 		}
+		if (ifs->ifa.ifa_addr)
+			gen_netmask(&ifs->ifa.ifa_netmask, ifa->ifa_family, &ifs->netmask, ifa->ifa_prefixlen);
+	}
+
+	if (ifs->ifa.ifa_name) {
+		if (!ctx->first) ctx->first = ifs;
+		if (ctx->last) ctx->last->ifa.ifa_next = &ifs->ifa;
+		ctx->last = ifs;
+	} else {
+		free(ifs);
 	}
-	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;
 }
 
+int getifaddrs(struct ifaddrs **ifap)
+{
+	struct ifaddrs_ctx _ctx, *ctx = &_ctx;
+	int r;
+	memset(ctx, 0, sizeof *ctx);
+	r = __rtnetlink_enumerate(AF_UNSPEC, AF_UNSPEC, netlink_msg_to_ifaddr, ctx);
+	if (r == 0) *ifap = &ctx->first->ifa;
+	else freeifaddrs(&ctx->first->ifa);
+	return r;
+}