add support for reverse name lookups from hosts file to getnameinfo

this also affects the legacy gethostbyaddr family, which uses
getnameinfo as its backend.

some other minor changes associated with the refactoring of source
files are also made; in particular, the resolv.conf parser now uses
the same code that's used elsewhere to handle ip literals, so as a
side effect it can now accept a scope id for nameserver addressed with
link-local scope.

1 files changed, 53 insertions, 5 deletions

diff --git a/src/network/getnameinfo.c b/src/network/getnameinfo.c
index 6962ed1a..708ec5e0 100644
--- a/src/network/getnameinfo.c
+++ b/src/network/getnameinfo.c
@@ -6,6 +6,9 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <net/if.h>
+#include <ctype.h>
+#include "lookup.h"
+#include "stdio_impl.h"
 
 int __dns_parse(const unsigned char *, int, int (*)(void *, int, const void *, int, const void *), void *);
 int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
@@ -42,6 +45,47 @@ static void mkptr6(char *s, const unsigned char *ip)
 	strcpy(s, "ip6.arpa");
 }
 
+static char *reverse_hosts(char *buf, const unsigned char *a, unsigned scopeid, int family)
+{
+	char line[512], *p, *z;
+	unsigned char _buf[1032], atmp[16];
+	struct address iplit;
+	FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
+	if (!f) return 0;
+	if (family == AF_INET) {
+		memcpy(atmp+12, a, 4);
+		memcpy(atmp, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
+		a = atmp;
+	}
+	while (fgets(line, sizeof line, f)) {
+		if ((p=strchr(line, '#'))) *p++='\n', *p=0;
+
+		for (p=line; *p && !isspace(*p); p++);
+		*p++ = 0;
+		if (__lookup_ipliteral(&iplit, line, AF_UNSPEC)<=0)
+			continue;
+
+		if (iplit.family == AF_INET) {
+			memcpy(iplit.addr+12, iplit.addr, 4);
+			memcpy(iplit.addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
+			iplit.scopeid = 0;
+		}
+
+		if (memcmp(a, iplit.addr, 16) || iplit.scopeid != scopeid)
+			continue;
+			
+		for (; *p && isspace(*p); p++);
+		for (z=p; *z && !isspace(*z); z++);
+		*z = 0;
+		if (z-p < 256) {
+			memcpy(buf, p, z-p+1);
+			break;
+		}
+	}
+	__fclose_ca(f);
+	return 0;
+}
+
 static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
 {
 	char tmp[256];
@@ -62,13 +106,14 @@ int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
 	char buf[256], num[3*sizeof(int)+1];
 	int af = sa->sa_family;
 	unsigned char *a;
-	unsigned x;
+	unsigned scopeid;
 
 	switch (af) {
 	case AF_INET:
 		a = (void *)&((struct sockaddr_in *)sa)->sin_addr;
 		if (sl != sizeof(struct sockaddr_in)) return EAI_FAMILY;
 		mkptr4(ptr, a);
+		scopeid = 0;
 		break;
 	case AF_INET6:
 		a = (void *)&((struct sockaddr_in6 *)sa)->sin6_addr;
@@ -77,6 +122,7 @@ int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
 			mkptr6(ptr, a);
 		else
 			mkptr4(ptr, a+12);
+		scopeid = ((struct sockaddr_in6 *)sa)->sin6_scope_id;
 		break;
 	default:
 		return EAI_FAMILY;
@@ -85,6 +131,9 @@ int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
 	if (node && nodelen) {
 		buf[0] = 0;
 		if (!(flags & NI_NUMERICHOST)) {
+			reverse_hosts(buf, a, scopeid, af);
+		}
+		if (!*buf && !(flags & NI_NUMERICHOST)) {
 			unsigned char query[18+PTR_MAX], reply[512];
 			int qlen = __res_mkquery(0, ptr, 1, RR_PTR,
 				0, 0, 0, query, sizeof query);
@@ -96,15 +145,14 @@ int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
 		if (!*buf) {
 			if (flags & NI_NAMEREQD) return EAI_NONAME;
 			inet_ntop(af, a, buf, sizeof buf);
-			if (af == AF_INET6 &&
-			    (x = ((struct sockaddr_in6 *)sa)->sin6_scope_id)) {
+			if (scopeid) {
 				char *p = 0, tmp[IF_NAMESIZE+1];
 				if (!(flags & NI_NUMERICSCOPE) &&
 				    (IN6_IS_ADDR_LINKLOCAL(a) ||
 				     IN6_IS_ADDR_MC_LINKLOCAL(a)))
-					p = if_indextoname(x, tmp+1);
+					p = if_indextoname(scopeid, tmp+1);
 				if (!p)
-					p = itoa(num, x);
+					p = itoa(num, scopeid);
 				*--p = '%';
 				strcat(buf, p);
 			}