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#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.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, 256)-1 > 254 || mbstowcs(0, host, 0) > 255) 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;
}
int __inet_aton(const char *, struct in_addr *);
static int name_from_numeric(struct address buf[static 1], const char *name, int family)
{
struct in_addr a4;
struct in6_addr a6;
if (family != AF_INET6 && __inet_aton(name, &a4)>0) {
memcpy(&buf[0].addr, &a4, sizeof a4);
buf[0].family = AF_INET;
return 1;
}
if (family != AF_INET && inet_pton(AF_INET6, name, &a6)>0) {
memcpy(&buf[0].addr, &a6, sizeof a6);
buf[0].family = AF_INET6;
return 1;
}
return 0;
}
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) return 0;
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;
memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
break;
case RR_AAAA:
if (len != 16) return -1;
ctx->addrs[ctx->cnt].family = AF_INET6;
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;
}
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) {
size_t l;
if ((l = strnlen(name, 256))-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<=0) cnt = name_from_numeric(buf, name, family);
if (cnt<=0 && !(flags & AI_NUMERICHOST)) {
cnt = name_from_hosts(buf, canon, name, family);
if (cnt<=0) 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].scopeid = 0;
buf[i].family = AF_INET6;
}
}
return cnt;
}
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