#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;
}
