Add local_addresses() to enumerate the local host's interface addresses (tested on all supported platforms except Windows)

src/inet.c

@@ -5,11 +5,27 @@
 #include <stdio.h>
 #include <string.h>
 
+#ifndef _WIN32
+  #include <sys/ioctl.h>
+  #include <sys/types.h>
+  #include <sys/socket.h>
+  #include <net/if.h>
+  #include <ifaddrs.h>
+#endif
+
 #include "lua.h"
 #include "lauxlib.h"
 
 #include "inet.h"
 
+typedef union {
+    struct sockaddr_storage sas;
+    struct sockaddr sa;
+    struct sockaddr_in sa4;
+    struct sockaddr_in6 sa6;
+} SA_union;
+
+
 /*=========================================================================*\
 * Internal function prototypes.
 \*=========================================================================*/
@@ -17,11 +33,12 @@ static int inet_global_toip(lua_State *L);
 static int inet_global_getaddrinfo(lua_State *L);
 static int inet_global_tohostname(lua_State *L);
 static int inet_global_getnameinfo(lua_State *L);
+static int inet_global_local_addresses(lua_State *L);
 static void inet_pushresolved(lua_State *L, struct hostent *hp);
 static int inet_global_gethostname(lua_State *L);
 
 /* DNS functions */
-static luaL_Reg func[] = {
+static luaL_Reg dns[] = {
     { "toip", inet_global_toip},
     { "getaddrinfo", inet_global_getaddrinfo},
     { "tohostname", inet_global_tohostname},
@@ -30,6 +47,12 @@ static luaL_Reg func[] = {
     { NULL, NULL}
 };
 
+/* global functions */
+static luaL_Reg func[] = {
+    { "local_addresses", inet_global_local_addresses},
+    { NULL, NULL}
+};
+
 /*=========================================================================*\
 * Exported functions
 \*=========================================================================*/
@@ -40,8 +63,11 @@ int inet_open(lua_State *L)
 {
     lua_pushstring(L, "dns");
     lua_newtable(L);
-    luaL_openlib(L, NULL, func, 0);
+    luaL_openlib(L, NULL, dns, 0);
     lua_settable(L, -3);
+
+    /* Export as global functions */
+    luaL_openlib(L, NULL, func, 0);
     return 0;
 }
 
@@ -221,6 +247,79 @@ static int inet_global_gethostname(lua_State *L)
     }
 }
 
+/*-------------------------------------------------------------------------*\
+* Enumerate all locally configured IP addresses
+\*-------------------------------------------------------------------------*/
+
+const char * const type_strings[] = {
+    "both",
+    "ipv4",
+    "ipv6",
+    NULL
+};
+
+int inet_global_local_addresses(lua_State *L)
+{
+    /* Link-local IPv4 addresses; see RFC 3927 and RFC 5735 */
+    const long ip4_linklocal = htonl(0xa9fe0000); /* 169.254.0.0 */
+    const long ip4_mask      = htonl(0xffff0000);
+#ifndef _WIN32
+    struct ifaddrs *addr = NULL, *a;
+    int n = 1;
+#endif
+    int type = luaL_checkoption(L, 1, "both", type_strings);
+    const char link_local = lua_toboolean(L, 2); /* defaults to 0 (false) */
+    const char ipv4 = (type == 0 || type == 1);
+    const char ipv6 = (type == 0 || type == 2);
+
+#ifndef _WIN32
+    if (getifaddrs(&addr) < 0) {
+        lua_pushnil(L);
+        lua_pushfstring(L, "getifaddrs failed (%d): %s", errno,
+                strerror(errno));
+        return 2;
+    }
+
+    lua_newtable(L);
+
+    for (a = addr; a; a = a->ifa_next) {
+        int family;
+        char ipaddr[INET6_ADDRSTRLEN];
+        const char *tmp = NULL;
+
+        if (a->ifa_addr == NULL || a->ifa_flags & IFF_LOOPBACK)
+            continue;
+
+        family = a->ifa_addr->sa_family;
+
+        if (ipv4 && family == AF_INET) {
+            struct sockaddr_in *sa = (struct sockaddr_in *)a->ifa_addr;
+            if (!link_local &&
+                    ((sa->sin_addr.s_addr & ip4_mask) == ip4_linklocal))
+                continue;
+            tmp = inet_ntop(family, &sa->sin_addr, ipaddr, sizeof(ipaddr));
+        } else if (ipv6 && family == AF_INET6) {
+            struct sockaddr_in6 *sa = (struct sockaddr_in6 *)a->ifa_addr;
+            if (!link_local && IN6_IS_ADDR_LINKLOCAL(&sa->sin6_addr))
+                continue;
+            if (IN6_IS_ADDR_V4MAPPED(&sa->sin6_addr) || IN6_IS_ADDR_V4COMPAT(&sa->sin6_addr))
+                continue;
+            tmp = inet_ntop(family, &sa->sin6_addr, ipaddr, sizeof(ipaddr));
+        }
+
+        if (tmp != NULL) {
+            lua_pushstring(L, tmp);
+            lua_rawseti(L, -2, n++);
+        }
+        /* TODO: Error reporting? */
+    }
+
+    freeifaddrs(addr);
+
+    return 1;
+#endif
+}
+
 
 
 /*=========================================================================*\