factor resolv.conf parsing out of res_msend to its own file

this change is made in preparation for adding search domains, for
which higher-level code will need to parse resolv.conf. simply parsing
it twice for each lookup would be one reasonable option, but the
existing parser code was buggy anyway, which suggested to me that it's
a bad idea to have two variants of this code in two different places.

the old code in res_msend potentially misinterpreted overly long lines
in resolv.conf, and stopped parsing after it found 3 nameservers, even
if there were relevant options left to be parsed later in the file.

1 files changed, 22 insertions, 60 deletions

diff --git a/src/network/res_msend.c b/src/network/res_msend.c
index d0e8e481..0ee914d4 100644
--- a/src/network/res_msend.c
+++ b/src/network/res_msend.c
@@ -31,14 +31,11 @@ int __res_msend(int nqueries, const unsigned char *const *queries,
 	const int *qlens, unsigned char *const *answers, int *alens, int asize)
 {
 	int fd;
-	FILE *f, _f;
-	unsigned char _buf[256];
-	char line[64], *s, *z;
-	int timeout = 5000, attempts = 2, retry_interval, servfail_retry;
+	int timeout, attempts, retry_interval, servfail_retry;
 	union {
 		struct sockaddr_in sin;
 		struct sockaddr_in6 sin6;
-	} sa = {0}, ns[3] = {{0}};
+	} sa = {0}, ns[MAXNS] = {{0}};
 	socklen_t sl = sizeof sa.sin;
 	int nns = 0;
 	int family = AF_INET;
@@ -48,65 +45,30 @@ int __res_msend(int nqueries, const unsigned char *const *queries,
 	int cs;
 	struct pollfd pfd;
 	unsigned long t0, t1, t2;
-	struct address iplit;
+	struct resolvconf conf;
 
 	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
 
-	/* Get nameservers from resolv.conf, fallback to localhost */
-	f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf);
-	if (!f) switch (errno) {
-	case ENOENT:
-	case ENOTDIR:
-	case EACCES:
-		goto no_resolv_conf;
-	default:
-		return -1;
-	}
-	for (nns=0; nns<3 && fgets(line, sizeof line, f); ) {
-		if (!strncmp(line, "options", 7) && isspace(line[7])) {
-			unsigned long x;
-			char *p, *z;
-			p = strstr(line, "timeout:");
-			if (p && isdigit(p[8])) {
-				p += 8;
-				x = strtoul(p, &z, 10);
-				if (z != p) timeout = x < 30 ? x*1000 : 30000;
-			}
-			p = strstr(line, "attempts:");
-			if (p && isdigit(p[9])) {
-				p += 9;
-				x = strtoul(p, &z, 10);
-				if (z != p) attempts = x < 10 ? x : 10;
-				if (!attempts) attempts = 1;
-			}
+	/* Get nameservers & timeout/retry settings from resolv.conf */
+	if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
+
+	timeout = 1000*conf.timeout;
+	attempts = conf.attempts;
+
+	nns = conf.nns;
+	for (nns=0; nns<conf.nns; nns++) {
+		struct address *iplit = &conf.ns[nns];
+		if (iplit->family == AF_INET) {
+			memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
+			ns[nns].sin.sin_port = htons(53);
+			ns[nns].sin.sin_family = AF_INET;
+		} else {
+			sl = sizeof sa.sin6;
+			memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
+			ns[nns].sin6.sin6_port = htons(53);
+			ns[nns].sin6.sin6_scope_id = iplit->scopeid;
+			ns[nns].sin6.sin6_family = family = AF_INET6;
 		}
-		if (strncmp(line, "nameserver", 10) || !isspace(line[10]))
-			continue;
-		for (s=line+11; isspace(*s); s++);
-		for (z=s; *z && !isspace(*z); z++);
-		*z=0;
-
-		if (__lookup_ipliteral(&iplit, s, AF_UNSPEC)>0) {
-			if (iplit.family == AF_INET) {
-				memcpy(&ns[nns].sin.sin_addr, iplit.addr, 4);
-				ns[nns].sin.sin_port = htons(53);
-				ns[nns++].sin.sin_family = AF_INET;
-			} else {
-				sl = sizeof sa.sin6;
-				memcpy(&ns[nns].sin6.sin6_addr, iplit.addr, 16);
-				ns[nns].sin6.sin6_port = htons(53);
-				ns[nns].sin6.sin6_scope_id = iplit.scopeid;
-				ns[nns++].sin6.sin6_family = family = AF_INET6;
-			}
-		}
-	}
-	__fclose_ca(f);
-no_resolv_conf:
-	if (!nns) {
-		ns[0].sin.sin_family = AF_INET;
-		ns[0].sin.sin_port = htons(53);
-		ns[0].sin.sin_addr.s_addr = htonl(0x7f000001);
-		nns=1;
 	}
 
 	/* Get local address and open/bind a socket */