github.com/afumu/libc@v0.0.6/musl/src/network/getnameinfo.c

#include <netdb.h>
#include <limits.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <ctype.h>
#include <resolv.h>
#include "lookup.h"
#include "stdio_impl.h"

#define PTR_MAX (64 + sizeof ".in-addr.arpa")
#define RR_PTR 12

static char *itoa(char *p, unsigned x) {
	p += 3*sizeof(int);
	*--p = 0;
	do {
		*--p = '0' + x % 10;
		x /= 10;
	} while (x);
	return p;
}

static void mkptr4(char *s, const unsigned char *ip)
{
	sprintf(s, "%d.%d.%d.%d.in-addr.arpa",
		ip[3], ip[2], ip[1], ip[0]);
}

static void mkptr6(char *s, const unsigned char *ip)
{
	static const char xdigits[] = "0123456789abcdef";
	int i;
	for (i=15; i>=0; i--) {
		*s++ = xdigits[ip[i]&15]; *s++ = '.';
		*s++ = xdigits[ip[i]>>4]; *s++ = '.';
	}
	strcpy(s, "ip6.arpa");
}

static void 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;
	//TODO FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
	FILE *f = fopen("/etc/hosts", "rb");
	if (!f) return;
	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;
		}
	}
	//TODO __fclose_ca(f);
	fclose(f);
}

static void reverse_services(char *buf, int port, int dgram)
{
	abort(); //TODO-
	// unsigned long svport;
	// char line[128], *p, *z;
	// unsigned char _buf[1032];
	// FILE _f, *f = __fopen_rb_ca("/etc/services", &_f, _buf, sizeof _buf);
	// if (!f) return;
	// while (fgets(line, sizeof line, f)) {
	// 	if ((p=strchr(line, '#'))) *p++='\n', *p=0;

	// 	for (p=line; *p && !isspace(*p); p++);
	// 	if (!*p) continue;
	// 	*p++ = 0;
	// 	svport = strtoul(p, &z, 10);

	// 	if (svport != port || z==p) continue;
	// 	if (dgram && strncmp(z, "/udp", 4)) continue;
	// 	if (!dgram && strncmp(z, "/tcp", 4)) continue;
	// 	if (p-line > 32) continue;

	// 	memcpy(buf, line, p-line);
	// 	break;
	// }
	// __fclose_ca(f);
}

static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
{
	abort(); //TODO-
	// if (rr != RR_PTR) return 0;
	// if (__dn_expand(packet, (const unsigned char *)packet + 512,
	//     data, c, 256) <= 0)
	// 	*(char *)c = 0;
	// return 0;
	
}

int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
	char *restrict node, socklen_t nodelen,
	char *restrict serv, socklen_t servlen,
	int flags)
{
	char ptr[PTR_MAX];
	char buf[256], num[3*sizeof(int)+1];
	int af = sa->sa_family;
	unsigned char *a;
	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;
		if (sl < sizeof(struct sockaddr_in6)) return EAI_FAMILY;
		if (memcmp(a, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12))
			mkptr6(ptr, a);
		else
			mkptr4(ptr, a+12);
		scopeid = ((struct sockaddr_in6 *)sa)->sin6_scope_id;
		break;
	default:
		return EAI_FAMILY;
	}

	if (node && nodelen) {
		buf[0] = 0;
		if (!(flags & NI_NUMERICHOST)) {
			reverse_hosts(buf, a, scopeid, af);
		}
		if (!*buf && !(flags & NI_NUMERICHOST)) {
			abort(); //TODO-
			// unsigned char query[18+PTR_MAX], reply[512];
			// int qlen = __res_mkquery(0, ptr, 1, RR_PTR,
			// 	0, 0, 0, query, sizeof query);
			// query[3] = 0; /* don't need AD flag */
			// int rlen = __res_send(query, qlen, reply, sizeof reply);
			// buf[0] = 0;
			// if (rlen > 0)
			// 	__dns_parse(reply, rlen, dns_parse_callback, buf);
		}
		if (!*buf) {
			if (flags & NI_NAMEREQD) return EAI_NONAME;
			inet_ntop(af, a, buf, sizeof buf);
			if (scopeid) {
				abort(); //TODO-
				// 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(scopeid, tmp+1);
				// if (!p)
				// 	p = itoa(num, scopeid);
				// *--p = '%';
				// strcat(buf, p);
			}
		}
		if (strlen(buf) >= nodelen) return EAI_OVERFLOW;
		strcpy(node, buf);
	}

	if (serv && servlen) {
		char *p = buf;
		int port = ntohs(((struct sockaddr_in *)sa)->sin_port);
		buf[0] = 0;
		if (!(flags & NI_NUMERICSERV))
			reverse_services(buf, port, flags & NI_DGRAM);
		if (!*p)
			p = itoa(num, port);
		if (strlen(p) >= servlen)
			return EAI_OVERFLOW;
		strcpy(serv, p);
	}

	return 0;
}