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

fusl/src/network/lookup_name.c

Index: fusl/src/network/lookup_name.c
diff --git a/fusl/src/network/lookup_name.c b/fusl/src/network/lookup_name.c
new file mode 100644
index 0000000000000000000000000000000000000000..df9e623e3a8891c3d6c4d3c56602a7df0f87c27f
--- /dev/null
+++ b/fusl/src/network/lookup_name.c
@@ -0,0 +1,345 @@
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <net/if.h>
+#include <arpa/inet.h>
+#include <ctype.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <errno.h>
+#include "lookup.h"
+#include "stdio_impl.h"
+#include "syscall.h"
+
+static int is_valid_hostname(const char *host)
+{
+	const unsigned char *s;
+	if (strnlen(host, 255)-1 >= 254 || mbstowcs(0, host, 0) == -1) return 0;
+	for (s=(void *)host; *s>=0x80 || *s=='.' || *s=='-' || isalnum(*s); s++);
+	return !*s;
+}
+
+static int name_from_null(struct address buf[static 2], const char *name, int family, int flags)
+{
+	int cnt = 0;
+	if (name) return 0;
+	if (flags & AI_PASSIVE) {
+		if (family != AF_INET6)
+			buf[cnt++] = (struct address){ .family = AF_INET };
+		if (family != AF_INET)
+			buf[cnt++] = (struct address){ .family = AF_INET6 };
+	} else {
+		if (family != AF_INET6)
+			buf[cnt++] = (struct address){ .family = AF_INET, .addr = { 127,0,0,1 } };
+		if (family != AF_INET)
+			buf[cnt++] = (struct address){ .family = AF_INET6, .addr = { [15] = 1 } };
+	}
+	return cnt;
+}
+
+static int name_from_numeric(struct address buf[static 1], const char *name, int family)
+{
+	return __lookup_ipliteral(buf, name, family);
+}
+
+static int name_from_hosts(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
+{
+	char line[512];
+	size_t l = strlen(name);
+	int cnt = 0;
+	unsigned char _buf[1032];
+	FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
+	if (!f) switch (errno) {
+	case ENOENT:
+	case ENOTDIR:
+	case EACCES:
+		return 0;
+	default:
+		return EAI_SYSTEM;
+	}
+	while (fgets(line, sizeof line, f) && cnt < MAXADDRS) {
+		char *p, *z;
+
+		if ((p=strchr(line, '#'))) *p++='\n', *p=0;
+		for(p=line+1; (p=strstr(p, name)) &&
+			(!isspace(p[-1]) || !isspace(p[l])); p++);
+		if (!p) continue;
+
+		/* Isolate IP address to parse */
+		for (p=line; *p && !isspace(*p); p++);
+		*p++ = 0;
+		if (name_from_numeric(buf+cnt, line, family))
+			cnt++;
+
+		/* Extract first name as canonical name */
+		for (; *p && isspace(*p); p++);
+		for (z=p; *z && !isspace(*z); z++);
+		*z = 0;
+		if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
+	}
+	__fclose_ca(f);
+	return cnt;
+}
+
+struct dpc_ctx {
+	struct address *addrs;
+	char *canon;
+	int cnt;
+};
+
+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);
+int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
+int __res_msend(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int);
+
+#define RR_A 1
+#define RR_CNAME 5
+#define RR_AAAA 28
+
+static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
+{
+	char tmp[256];
+	struct dpc_ctx *ctx = c;
+	switch (rr) {
+	case RR_A:
+		if (len != 4) return -1;
+		ctx->addrs[ctx->cnt].family = AF_INET;
+		ctx->addrs[ctx->cnt].scopeid = 0;
+		memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
+		break;
+	case RR_AAAA:
+		if (len != 16) return -1;
+		ctx->addrs[ctx->cnt].family = AF_INET6;
+		ctx->addrs[ctx->cnt].scopeid = 0;
+		memcpy(ctx->addrs[ctx->cnt++].addr, data, 16);
+		break;
+	case RR_CNAME:
+		if (__dn_expand(packet, (const unsigned char *)packet + 512,
+		    data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
+			strcpy(ctx->canon, tmp);
+		break;
+	}
+	return 0;
+}
+
+static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
+{
+	unsigned char qbuf[2][280], abuf[2][512];
+	const unsigned char *qp[2] = { qbuf[0], qbuf[1] };
+	unsigned char *ap[2] = { abuf[0], abuf[1] };
+	int qlens[2], alens[2];
+	int i, nq = 0;
+	struct dpc_ctx ctx = { .addrs = buf, .canon = canon };
+
+	if (family != AF_INET6) {
+		qlens[nq] = __res_mkquery(0, name, 1, RR_A, 0, 0, 0,
+			qbuf[nq], sizeof *qbuf);
+		nq++;
+	}
+	if (family != AF_INET) {
+		qlens[nq] = __res_mkquery(0, name, 1, RR_AAAA, 0, 0, 0,
+			qbuf[nq], sizeof *qbuf);
+		nq++;
+	}
+
+	if (__res_msend(nq, qp, qlens, ap, alens, sizeof *abuf) < 0) return EAI_SYSTEM;
+
+	for (i=0; i<nq; i++)
+		__dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
+
+	if (ctx.cnt) return ctx.cnt;
+	if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
+	if ((abuf[0][3] & 15) == 3) return EAI_NONAME;
+	return EAI_FAIL;
+}
+
+static const struct policy {
+	unsigned char addr[16];
+	unsigned char len, mask;
+	unsigned char prec, label;
+} defpolicy[] = {
+	{ "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 },
+	{ "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 },
+	{ "\x20\2", 1, 0xff, 30, 2 },
+	{ "\x20\1", 3, 0xff, 5, 5 },
+	{ "\xfc", 0, 0xfe, 3, 13 },
+#if 0
+	/* These are deprecated and/or returned to the address
+	 * pool, so despite the RFC, treating them as special
+	 * is probably wrong. */
+	{ "", 11, 0xff, 1, 3 },
+	{ "\xfe\xc0", 1, 0xc0, 1, 11 },
+	{ "\x3f\xfe", 1, 0xff, 1, 12 },
+#endif
+	/* Last rule must match all addresses to stop loop. */
+	{ "", 0, 0, 40, 1 },
+};
+
+static const struct policy *policyof(const struct in6_addr *a)
+{
+	int i;
+	for (i=0; ; i++) {
+		if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len))
+			continue;
+		if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask)
+		    != defpolicy[i].addr[defpolicy[i].len])
+			continue;
+		return defpolicy+i;
+	}
+}
+
+static int labelof(const struct in6_addr *a)
+{
+	return policyof(a)->label;
+}
+
+static int scopeof(const struct in6_addr *a)
+{
+	if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15;
+	if (IN6_IS_ADDR_LINKLOCAL(a)) return 2;
+	if (IN6_IS_ADDR_LOOPBACK(a)) return 2;
+	if (IN6_IS_ADDR_SITELOCAL(a)) return 5;
+	return 14;
+}
+
+static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d)
+{
+	/* FIXME: The common prefix length should be limited to no greater
+	 * than the nominal length of the prefix portion of the source
+	 * address. However the definition of the source prefix length is
+	 * not clear and thus this limiting is not yet implemented. */
+	unsigned i;
+	for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++);
+	return i;
+}
+
+#define DAS_USABLE              0x40000000
+#define DAS_MATCHINGSCOPE       0x20000000
+#define DAS_MATCHINGLABEL       0x10000000
+#define DAS_PREC_SHIFT          20
+#define DAS_SCOPE_SHIFT         16
+#define DAS_PREFIX_SHIFT        8
+#define DAS_ORDER_SHIFT         0
+
+static int addrcmp(const void *_a, const void *_b)
+{
+	const struct address *a = _a, *b = _b;
+	return b->sortkey - a->sortkey;
+}
+
+int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)
+{
+	int cnt = 0, i, j;
+
+	*canon = 0;
+	if (name) {
+		/* reject empty name and check len so it fits into temp bufs */
+		size_t l = strnlen(name, 255);
+		if (l-1 >= 254)
+			return EAI_NONAME;
+		memcpy(canon, name, l+1);
+	}
+
+	/* Procedurally, a request for v6 addresses with the v4-mapped
+	 * flag set is like a request for unspecified family, followed
+	 * by filtering of the results. */
+	if (flags & AI_V4MAPPED) {
+		if (family == AF_INET6) family = AF_UNSPEC;
+		else flags -= AI_V4MAPPED;
+	}
+
+	/* Try each backend until there's at least one result. */
+	cnt = name_from_null(buf, name, family, flags);
+	if (!cnt) cnt = name_from_numeric(buf, name, family);
+	if (!cnt && !(flags & AI_NUMERICHOST)) {
+		cnt = name_from_hosts(buf, canon, name, family);
+		if (!cnt) cnt = name_from_dns(buf, canon, name, family);
+	}
+	if (cnt<=0) return cnt ? cnt : EAI_NONAME;
+
+	/* Filter/transform results for v4-mapped lookup, if requested. */
+	if (flags & AI_V4MAPPED) {
+		if (!(flags & AI_ALL)) {
+			/* If any v6 results exist, remove v4 results. */
+			for (i=0; i<cnt && buf[i].family != AF_INET6; i++);
+			if (i<cnt) {
+				for (j=0; i<cnt; i++) {
+					if (buf[i].family == AF_INET6)
+						buf[j++] = buf[i];
+				}
+				cnt = i = j;
+			}
+		}
+		/* Translate any remaining v4 results to v6 */
+		for (i=0; i<cnt; i++) {
+			if (buf[i].family != AF_INET) continue;
+			memcpy(buf[i].addr+12, buf[i].addr, 4);
+			memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
+			buf[i].family = AF_INET6;
+		}
+	}
+
+	/* No further processing is needed if there are fewer than 2
+	 * results or if there are only IPv4 results. */
+	if (cnt<2 || family==AF_INET) return cnt;
+	for (i=0; buf[i].family == AF_INET; i++)
+		if (i==cnt) return cnt;
+
+	int cs;
+	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+
+	/* The following implements a subset of RFC 3484/6724 destination
+	 * address selection by generating a single 31-bit sort key for
+	 * each address. Rules 3, 4, and 7 are omitted for having
+	 * excessive runtime and code size cost and dubious benefit.
+	 * So far the label/precedence table cannot be customized. */
+	for (i=0; i<cnt; i++) {
+		int key = 0;
+		struct sockaddr_in6 sa, da = {
+			.sin6_family = AF_INET6,
+			.sin6_scope_id = buf[i].scopeid,
+			.sin6_port = 65535
+		};
+		if (buf[i].family == AF_INET6) {
+			memcpy(da.sin6_addr.s6_addr, buf[i].addr, 16);
+		} else {
+			memcpy(da.sin6_addr.s6_addr,
+				"\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
+			memcpy(da.sin6_addr.s6_addr+12, buf[i].addr, 4);
+		}
+		const struct policy *dpolicy = policyof(&da.sin6_addr);
+		int dscope = scopeof(&da.sin6_addr);
+		int dlabel = dpolicy->label;
+		int dprec = dpolicy->prec;
+		int prefixlen = 0;
+		int fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP);
+		if (fd >= 0) {
+			if (!connect(fd, (void *)&da, sizeof da)) {
+				key |= DAS_USABLE;
+				if (!getsockname(fd, (void *)&sa,
+				    &(socklen_t){sizeof sa})) {
+					if (dscope == scopeof(&sa.sin6_addr))
+						key |= DAS_MATCHINGSCOPE;
+					if (dlabel == labelof(&sa.sin6_addr))
+						key |= DAS_MATCHINGLABEL;
+					prefixlen = prefixmatch(&sa.sin6_addr,
+						&da.sin6_addr);
+				}
+			}
+			close(fd);
+		}
+		key |= dprec << DAS_PREC_SHIFT;
+		key |= (15-dscope) << DAS_SCOPE_SHIFT;
+		key |= prefixlen << DAS_PREFIX_SHIFT;
+		key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
+		buf[i].sortkey = key;
+	}
+	qsort(buf, cnt, sizeof *buf, addrcmp);
+
+	pthread_setcancelstate(cs, 0);
+
+	return cnt;
+}