Re: getaddrinfo(3) / AI_ADDRCONFIG

[Christopher Friedt <chrisfriedt@gmail.com>]

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On Wed, Jul 11, 2018 at 1:00 PM Rich Felker <dalias@libc.org> wrote:
> It could probably go inside __lookup_name, but maybe in getaddrinfo is
> better since that would avoid linking it for gethostbyname, etc.
> (which don't need it).

Done

> > inconsistent with musl (spaces
> > > after opening and before closing paren, etc.).

Done

> I think the one mandated by POSIX is EAI_NONAME ("The name does not
> resolve for the supplied parameters").

Done

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diff --git a/src/network/getaddrinfo.c b/src/network/getaddrinfo.c
index b9439f77..72276ddc 100644
--- a/src/network/getaddrinfo.c
+++ b/src/network/getaddrinfo.c
@@ -1,8 +1,10 @@
+#include <stdbool.h>
 #include <stdlib.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <netdb.h>
 #include <string.h>
+#include <unistd.h>
 #include "lookup.h"
 
 int getaddrinfo(const char *restrict host, const char *restrict serv, const struct addrinfo *restrict hint, struct addrinfo **restrict res)
@@ -10,7 +12,7 @@ int getaddrinfo(const char *restrict host, const char *restrict serv, const stru
 	struct service ports[MAXSERVS];
 	struct address addrs[MAXADDRS];
 	char canon[256], *outcanon;
-	int nservs, naddrs, nais, canon_len, i, j, k;
+	int nservs, naddrs, nais, canon_len, i, j, k, fd, r;
 	int family = AF_UNSPEC, flags = 0, proto = 0, socktype = 0;
 	struct aibuf {
 		struct addrinfo ai;
@@ -19,6 +21,11 @@ int getaddrinfo(const char *restrict host, const char *restrict serv, const stru
 			struct sockaddr_in6 sin6;
 		} sa;
 	} *out;
+	struct addrconfig {
+		bool af_inet;
+		bool af_inet6;
+	} addrconfig;
+	struct sockaddr_storage sas;
 
 	if (!host && !serv) return EAI_NONAME;
 
@@ -33,6 +40,35 @@ int getaddrinfo(const char *restrict host, const char *restrict serv, const stru
 		if ((flags & mask) != flags)
 			return EAI_BADFLAGS;
 
+		if (flags & AI_ADDRCONFIG) {
+			*((struct sockaddr_in *)(&sas)) = (struct sockaddr_in){
+				.sin_family = AF_INET,
+				.sin_port = htons(42),
+				.sin_addr.s_addr = INADDR_LOOPBACK,
+			};
+			addrconfig.af_inet = false;
+			r = socket(AF_INET, SOCK_DGRAM, 0);
+			if (-1 != r) {
+				fd = r;
+				r = connect(fd, (struct sockaddr *) & sas, sizeof( struct sockaddr_in ));
+				addrconfig.af_inet = 0 == r;
+				close(fd);
+			}
+			*((struct sockaddr_in6 *)(&sas)) = (struct sockaddr_in6){
+				.sin6_family = AF_INET6,
+				.sin6_port = htons(42),
+				.sin6_addr = IN6ADDR_LOOPBACK_INIT,
+			};
+			addrconfig.af_inet6 = false;
+			r = socket(AF_INET6, SOCK_DGRAM, 0);
+			if (-1 != r) {
+				fd = r;
+				r = connect(fd, (struct sockaddr *) & sas, sizeof(struct sockaddr_in6));
+				addrconfig.af_inet6 = 0 == r;
+				close(fd);
+			}
+		}
+
 		switch (family) {
 		case AF_INET:
 		case AF_INET6:
@@ -61,30 +97,43 @@ int getaddrinfo(const char *restrict host, const char *restrict serv, const stru
 		outcanon = 0;
 	}
 
-	for (k=i=0; i<naddrs; i++) for (j=0; j<nservs; j++, k++) {
-		out[k].ai = (struct addrinfo){
-			.ai_family = addrs[i].family,
-			.ai_socktype = ports[j].socktype,
-			.ai_protocol = ports[j].proto,
-			.ai_addrlen = addrs[i].family == AF_INET
-				? sizeof(struct sockaddr_in)
-				: sizeof(struct sockaddr_in6),
-			.ai_addr = (void *)&out[k].sa,
-			.ai_canonname = outcanon,
-			.ai_next = &out[k+1].ai };
+	for (k=i=0; i<naddrs; i++) for (j=0; j<nservs; j++) {
 		switch (addrs[i].family) {
 		case AF_INET:
+			if ((flags & AI_ADDRCONFIG) && !addrconfig.af_inet) {
+				nais--;
+				continue;
+			}
 			out[k].sa.sin.sin_family = AF_INET;
 			out[k].sa.sin.sin_port = htons(ports[j].port);
 			memcpy(&out[k].sa.sin.sin_addr, &addrs[i].addr, 4);
 			break;
 		case AF_INET6:
+			if ((flags & AI_ADDRCONFIG ) && !addrconfig.af_inet6) {
+				nais--;
+				continue;
+			}
 			out[k].sa.sin6.sin6_family = AF_INET6;
 			out[k].sa.sin6.sin6_port = htons(ports[j].port);
 			out[k].sa.sin6.sin6_scope_id = addrs[i].scopeid;
 			memcpy(&out[k].sa.sin6.sin6_addr, &addrs[i].addr, 16);
-			break;			
+			break;
 		}
+		out[k].ai = (struct addrinfo){
+			.ai_family = addrs[i].family,
+			.ai_socktype = ports[j].socktype,
+			.ai_protocol = ports[j].proto,
+			.ai_addrlen = addrs[i].family == AF_INET
+				? sizeof(struct sockaddr_in)
+				: sizeof(struct sockaddr_in6),
+			.ai_addr = (void *)&out[k].sa,
+			.ai_canonname = outcanon,
+			.ai_next = &out[k+1].ai };
+		k++;
+	}
+	if ( nais < 1 ) {
+		free( out );
+		return EAI_NONAME;
 	}
 	out[nais-1].ai.ai_next = 0;
 	*res = &out->ai;