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/* host.c - DNS lookup utility
*
* Copyright 2014 Rich Felker <dalias@aerifal.cx>
*
* No standard, but there's a version in bind9
USE_HOST(NEWTOY(host, "<1>2avt:", TOYFLAG_USR|TOYFLAG_BIN))
config HOST
bool "host"
default n
help
usage: host [-av] [-t TYPE] NAME [SERVER]
Perform DNS lookup on NAME, which can be a domain name to lookup,
or an IPv4 dotted or IPv6 colon-seperated address to reverse lookup.
SERVER (if present) is the DNS server to use.
-a no idea
-t not a clue
-v verbose
*/
#define FOR_host
#include "toys.h"
GLOBALS(
char *type_str;
)
#include <resolv.h>
#define PL_IP 1
#define PL_NAME 2
#define PL_DATA 3
#define PL_TEXT 4
#define PL_SOA 5
#define PL_MX 6
#define PL_SRV 7
static const struct rrt {
const char *name;
const char *msg;
int pl;
int af;
} rrt[] = {
[1] = { "A", "has address", PL_IP, AF_INET },
[28] = { "AAAA", "has address", PL_IP, AF_INET6 },
[2] = { "NS", "name server", PL_NAME },
[5] = { "CNAME", "is a nickname for", PL_NAME },
[16] = { "TXT", "descriptive text", PL_TEXT },
[6] = { "SOA", "start of authority", PL_SOA },
[12] = { "PTR", "domain name pointer", PL_NAME },
[15] = { "MX", "mail is handled", PL_MX },
[33] = { "SRV", "mail is handled", PL_SRV },
[255] = { "*", 0, 0 },
};
static const char rct[16][32] = {
"Success",
"Format error",
"Server failure",
"Non-existant domain",
"Not implemented",
"Refused",
};
void host_main(void)
{
int verbose=(toys.optflags & (FLAG_a|FLAG_v)), type,
i, j, ret, sec, count, rcode, qlen, alen, pllen = 0;
unsigned ttl, pri, v[5];
unsigned char qbuf[280], abuf[512], *p;
char *name, *nsname, rrname[256], plname[640], ptrbuf[128];
struct addrinfo *ai, iplit_hints = { .ai_flags = AI_NUMERICHOST };
name = *toys.optargs;
nsname = toys.optargs[1];
if (!TT.type_str && (toys.optflags & FLAG_a)) TT.type_str = "255";
if (!getaddrinfo(name, 0, &iplit_hints, &ai)) {
unsigned char *a;
static const char xdigits[] = "0123456789abcdef";
if (ai->ai_family == AF_INET) {
a = (void *)&((struct sockaddr_in *)ai->ai_addr)->sin_addr;
snprintf(ptrbuf, sizeof(ptrbuf), "%d.%d.%d.%d.in-addr.arpa",
a[3], a[2], a[1], a[0]);
} else if (ai->ai_family == AF_INET6) {
a = (void *)&((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr;
for (j=0, i=15; i>=0; i--) {
ptrbuf[j++] = xdigits[a[i]&15];
ptrbuf[j++] = '.';
ptrbuf[j++] = xdigits[a[i]>>4];
ptrbuf[j++] = '.';
}
strcpy(ptrbuf+j, "ip6.arpa");
}
name = ptrbuf;
if (!TT.type_str) TT.type_str="12";
} else if (!TT.type_str) TT.type_str="1";
if (TT.type_str[0]-'0' < 10u) type = atoi(TT.type_str);
else {
type = -1;
for (i=0; i < sizeof rrt / sizeof *rrt; i++) {
if (rrt[i].name && !strcasecmp(TT.type_str, rrt[i].name)) {
type = i;
break;
}
}
if (!strcasecmp(TT.type_str, "any")) type = 255;
if (type < 0) error_exit("Invalid query type: %s", TT.type_str);
}
qlen = res_mkquery(0, name, 1, type, 0, 0, 0, qbuf, sizeof qbuf);
if (qlen < 0) error_exit("Invalid query parameters: %s", name);
if (nsname) {
struct addrinfo ns_hints = { .ai_socktype = SOCK_DGRAM };
if ((ret = getaddrinfo(nsname, "53", &ns_hints, &ai)) < 0)
error_exit("Error looking up server name: %s", gai_strerror(ret));
int s = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
if (s < 0 || connect(s, ai->ai_addr, ai->ai_addrlen) < 0)
perror_exit("Socket error");
setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &(struct timeval){ .tv_sec = 5 },
sizeof(struct timeval));
printf("Using domain server %s:\n", nsname);
send(s, qbuf, qlen, 0);
alen = recv(s, abuf, sizeof abuf, 0);
} else alen = res_send(qbuf, qlen, abuf, sizeof abuf);
if (alen < 12) error_exit("Host not found.");
rcode = abuf[3] & 15;
if (verbose) {
printf("rcode = %d (%s), ancount = %d\n",
rcode, rct[rcode], 256*abuf[6] + abuf[7]);
if (!(abuf[2] & 4)) printf("The following answer is not authoritative:\n");
}
if (rcode) error_exit("Host not found.");
p = abuf + 12;
for (sec=0; sec<4; sec++) {
count = 256*abuf[4+2*sec] + abuf[5+2*sec];
if (verbose && count>0 && sec>1)
puts(sec==2 ? "For authoritative answers, see:"
: "Additional information:");
for (; count--; p += pllen) {
p += dn_expand(abuf, abuf+alen, p, rrname, sizeof(rrname));
type = (p[0]<<8) + p[1];
p += 4;
if (!sec) continue;
ttl = (p[0]<<24)+(p[1]<<16)+(p[2]<<8)+p[3];
p += 4;
pllen = (p[0]<<8) + p[1];
p += 2;
switch (type<sizeof(rrt)/sizeof(*rrt) ? rrt[type].pl : 0) {
case PL_IP:
inet_ntop(rrt[type].af, p, plname, sizeof plname);
break;
case PL_NAME:
dn_expand(abuf, abuf+alen, p, plname, sizeof plname);
break;
case PL_TEXT:
snprintf(plname, sizeof plname, "\"%.*s\"", pllen, p);
break;
case PL_SOA:
i = dn_expand(abuf, abuf+alen, p, plname, sizeof plname - 1);
strcat(plname, " ");
i += dn_expand(abuf, abuf+alen, p+i, plname+strlen(plname),
sizeof(plname)-strlen(plname));
for (j=0; j<5; j++)
v[j] = (p[i+4*j]<<24)+(p[1+i+4*j]<<16)+(p[2+i+4*j]<<8)+p[3+i+4*j];
snprintf(plname+strlen(plname), sizeof(plname)-strlen(plname),
"(\n\t\t%u\t;serial (version)\n"
"\t\t%u\t;refresh period\n"
"\t\t%u\t;retry interval\n"
"\t\t%u\t;expire time\n"
"\t\t%u\t;default ttl\n"
"\t\t)", v[0], v[1], v[2], v[3], v[4]);
break;
case PL_MX:
pri = (p[0]<<8)+p[1];
snprintf(plname, sizeof(plname), verbose ? "%d " : "(pri=%d) by ", pri);
dn_expand(abuf, abuf+alen, p+2, plname+strlen(plname),
sizeof plname - strlen(plname));
break;
case PL_SRV:
for (j=0; j<3; j++) v[j] = (p[2*j]<<8) + p[1+2*j];
snprintf(plname, sizeof(plname), "%u %u %u ", v[0], v[1], v[2]);
dn_expand(abuf, abuf+alen, p+6, plname+strlen(plname),
sizeof plname - strlen(plname));
break;
default:
printf("%s unsupported RR type %u\n", rrname, type);
continue;
}
if (verbose)
printf("%s\t%u\tIN %s\t%s\n", rrname, ttl, rrt[type].name, plname);
else if (rrt[type].msg)
printf("%s %s %s\n", rrname, rrt[type].msg, plname);
}
if (!verbose && sec==1) break;
}
toys.exitval = rcode;
}
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