Add a "fork" of musl as //fusl.

fusl/src/network/res_msend.c

Index: fusl/src/network/res_msend.c
diff --git a/fusl/src/network/res_msend.c b/fusl/src/network/res_msend.c
new file mode 100644
index 0000000000000000000000000000000000000000..d0e8e4815d0d87cfa44be2d845d0367913059cea
--- /dev/null
+++ b/fusl/src/network/res_msend.c
@@ -0,0 +1,218 @@
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <arpa/inet.h>
+#include <stdint.h>
+#include <string.h>
+#include <poll.h>
+#include <time.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <errno.h>
+#include <pthread.h>
+#include "stdio_impl.h"
+#include "syscall.h"
+#include "lookup.h"
+
+static void cleanup(void *p)
+{
+	__syscall(SYS_close, (intptr_t)p);
+}
+
+static unsigned long mtime()
+{
+	struct timespec ts;
+	clock_gettime(CLOCK_REALTIME, &ts);
+	return (unsigned long)ts.tv_sec * 1000
+		+ ts.tv_nsec / 1000000;
+}
+
+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;
+	union {
+		struct sockaddr_in sin;
+		struct sockaddr_in6 sin6;
+	} sa = {0}, ns[3] = {{0}};
+	socklen_t sl = sizeof sa.sin;
+	int nns = 0;
+	int family = AF_INET;
+	int rlen;
+	int next;
+	int i, j;
+	int cs;
+	struct pollfd pfd;
+	unsigned long t0, t1, t2;
+	struct address iplit;
+
+	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;
+			}
+		}
+		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 */
+	sa.sin.sin_family = family;
+	fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+
+	/* Handle case where system lacks IPv6 support */
+	if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
+		fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+		family = AF_INET;
+	}
+	if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) return -1;
+
+	/* Past this point, there are no errors. Each individual query will
+	 * yield either no reply (indicated by zero length) or an answer
+	 * packet which is up to the caller to interpret. */
+
+	pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
+	pthread_setcancelstate(cs, 0);
+
+	/* Convert any IPv4 addresses in a mixed environment to v4-mapped */
+	if (family == AF_INET6) {
+		setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
+		for (i=0; i<nns; i++) {
+			if (ns[i].sin.sin_family != AF_INET) continue;
+			memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
+				&ns[i].sin.sin_addr, 4);
+			memcpy(ns[i].sin6.sin6_addr.s6_addr,
+				"\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
+			ns[i].sin6.sin6_family = AF_INET6;
+			ns[i].sin6.sin6_flowinfo = 0;
+			ns[i].sin6.sin6_scope_id = 0;
+		}
+	}
+
+	memset(alens, 0, sizeof *alens * nqueries);
+
+	pfd.fd = fd;
+	pfd.events = POLLIN;
+	retry_interval = timeout / attempts;
+	next = 0;
+	t0 = t2 = mtime();
+	t1 = t2 - retry_interval;
+
+	for (; t2-t0 < timeout; t2=mtime()) {
+		if (t2-t1 >= retry_interval) {
+			/* Query all configured namservers in parallel */
+			for (i=0; i<nqueries; i++)
+				if (!alens[i])
+					for (j=0; j<nns; j++)
+						sendto(fd, queries[i],
+							qlens[i], MSG_NOSIGNAL,
+							(void *)&ns[j], sl);
+			t1 = t2;
+			servfail_retry = 2 * nqueries;
+		}
+
+		/* Wait for a response, or until time to retry */
+		if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
+
+		while ((rlen = recvfrom(fd, answers[next], asize, 0,
+		  (void *)&sa, (socklen_t[1]){sl})) >= 0) {
+
+			/* Ignore non-identifiable packets */
+			if (rlen < 4) continue;
+
+			/* Ignore replies from addresses we didn't send to */
+			for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
+			if (j==nns) continue;
+
+			/* Find which query this answer goes with, if any */
+			for (i=next; i<nqueries && (
+				answers[next][0] != queries[i][0] ||
+				answers[next][1] != queries[i][1] ); i++);
+			if (i==nqueries) continue;
+			if (alens[i]) continue;
+
+			/* Only accept positive or negative responses;
+			 * retry immediately on server failure, and ignore
+			 * all other codes such as refusal. */
+			switch (answers[next][3] & 15) {
+			case 0:
+			case 3:
+				break;
+			case 2:
+				if (servfail_retry && servfail_retry--)
+					sendto(fd, queries[i],
+						qlens[i], MSG_NOSIGNAL,
+						(void *)&ns[j], sl);
+			default:
+				continue;
+			}
+
+			/* Store answer in the right slot, or update next
+			 * available temp slot if it's already in place. */
+			alens[i] = rlen;
+			if (i == next)
+				for (; next<nqueries && alens[next]; next++);
+			else
+				memcpy(answers[i], answers[next], rlen);
+
+			if (next == nqueries) goto out;
+		}
+	}
+out:
+	pthread_cleanup_pop(1);
+
+	return 0;
+}