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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
* See https://www.ietf.org/rfc/rfc1035.txt
* See https://www.ietf.org/rfc/rfc3596.txt
USE_HOST(NEWTOY(host, "<1>2avt:", TOYFLAG_USR|TOYFLAG_BIN))
config HOST
bool "host"
default y
help
usage: host [-v] [-t TYPE] NAME [SERVER]
Look up DNS records for NAME, either domain name or IPv4/IPv6 address to
reverse lookup, from SERVER or default DNS server(s).
-a All records
-t TYPE Record TYPE (number or ANY A AAAA CNAME MX NS PTR SOA SRV TXT)
-v Verbose
*/
#define FOR_host
#include "toys.h"
#include <resolv.h>
GLOBALS(
char *t;
char **nsname;
unsigned nslen;
)
static const struct rrt {
char *name, *msg;
int type;
} rrt[] = { { "A", "has address", 1 }, { "NS", "name server", 2 },
{ "CNAME", "is a nickname for", 5 }, { "SOA", "start of authority", 6 },
{ "PTR", "domain name pointer", 12 }, { "HINFO", "host information", 13 },
{ "MX", "mail is handled", 15 }, { "TXT", "descriptive text", 16 },
{ "AAAA", "has address", 28 }, { "SRV", "mail is handled", 33 }
};
int xdn_expand(char *packet, char *endpkt, char *comp, char *expand, int elen)
{
int i = dn_expand(packet, endpkt, comp, expand, elen);
if (i<1) error_exit("bad dn_expand");
return i;
}
// Fetch "nameserve" lines from /etc/resolv.conf. Ignores 'options' lines
static void get_nsname(char **pline, long len)
{
char *line, *p;
if (!len) return;
line = *pline;
if (strstart(&line, "nameserver") && isspace(*line)) {
while (isspace(*line)) line++;
for (p = line; *p && !isspace(*p) && *p!='#'; p++);
if (p == line) return;
*p = 0;
if (!(TT.nslen&8))
TT.nsname = xrealloc(TT.nsname, (TT.nslen+8)*sizeof(void *));
TT.nsname[TT.nslen++] = xstrdup(line);
}
}
void host_main(void)
{
int verbose = FLAG(a)||FLAG(v), type, abuf_len = 65536, //Largest TCP response
i, j, sec, rcode, qlen, alen QUIET, pllen = 0, t2len = 2048;
unsigned count, ttl;
char *abuf = xmalloc(abuf_len), *name = *toys.optargs, *p, *ss,
*t2 = toybuf+t2len;
struct addrinfo *ai;
// What kind of query are we doing?
if (!TT.t && FLAG(a)) TT.t = "255";
if (!getaddrinfo(name, 0,&(struct addrinfo){.ai_flags=AI_NUMERICHOST}, &ai)) {
name = toybuf;
if (ai->ai_family == AF_INET) {
p = (void *)&((struct sockaddr_in *)ai->ai_addr)->sin_addr;
sprintf(name, "%d.%d.%d.%d.in-addr.arpa", p[3], p[2], p[1], p[0]);
} else if (ai->ai_family == AF_INET6) {
p = (void *)&((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr;
for (j = 0, i = 15; i>=0; i--)
j += sprintf(name+j, "%x.%x.", p[i]&15, p[i]>>4);
strcpy(name+j, "ip6.arpa");
}
if (!TT.t) TT.t = "12";
} else if (!TT.t) TT.t = "1";
// Prepare query packet of appropriate type
if (TT.t[0]-'0'<10) type = atoi(TT.t); // TODO
else if (!strcasecmp(TT.t, "any") || !strcmp(TT.t, "*")) type = 255;
else {
for (i = 0; i<ARRAY_LEN(rrt); i++) if (!strcasecmp(TT.t, rrt[i].name)) {
type = rrt[i].type;
break;
}
if (i == ARRAY_LEN(rrt)) error_exit("bad -t: %s", TT.t);
}
qlen = res_mkquery(0, name, 1, type, 0, 0, 0, t2, 280); //t2len);
if (qlen<0) error_exit("bad NAME: %s", name);
// Grab nameservers
if (toys.optargs[1]) TT.nsname = toys.optargs+1;
else do_lines(xopen("/etc/resolv.conf", O_RDONLY), '\n', get_nsname);
if (!TT.nsname) error_exit("No nameservers");
// Send one query packet to each server until we receive response
while (*TT.nsname) {
if (verbose) printf("Using domain server %s:\n", *TT.nsname);
ai = xgetaddrinfo(*TT.nsname, "53", 0, SOCK_DGRAM, 0, 0);
i = xsocket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
xconnect(i, ai->ai_addr, ai->ai_addrlen);
setsockopt(i, SOL_SOCKET, SO_RCVTIMEO, &(struct timeval){ .tv_sec = 5 },
sizeof(struct timeval));
send(i, t2, qlen, 0);
if (16 < (alen = recv(i, abuf, abuf_len, 0))) break;
if (!*++TT.nsname) error_exit("Host not found.");
close(i);
}
// Did it error?
rcode = abuf[3]&7;
if (verbose) {
printf("rcode = %d, ancount = %d\n", rcode, (int)peek_be(abuf+6, 2));
if (!(abuf[2]&4)) puts("The following answer is not authoritative:");
}
if (rcode) error_exit("Host not found: %s",
(char *[]){ "Format error", "Server failure",
"Non-existant domain", "Not implemented", "Refused", ""}[rcode-1]);
// Print the result
p = abuf + 12;
qlen = 0;
for (sec = 0; sec<(2<<verbose); sec++) {
count = peek_be(abuf+4+2*sec, 2);
if (verbose && count>0 && sec>1)
puts(sec==2 ? "For authoritative answers, see:"
: "Additional information:");
for (; count--; p += pllen) {
p += xdn_expand(abuf, abuf+alen, p, toybuf, 4096-t2len);
if (alen-(p-abuf)<10) error_exit("tilt");
type = peek_be(p, 2);
p += 4;
if (!sec) continue;
ttl = peek_be(p, 4);
p += 4;
pllen = peek_be(p, 2);
p += 2;
if ((p-abuf)+pllen>alen) error_exit("tilt");
if (type==1 || type == 28)
inet_ntop(type==1 ? AF_INET : AF_INET6, p, t2, t2len);
else if (type==2 || type==5) xdn_expand(abuf, abuf+alen, p, t2, t2len);
else if (type==13 || type==16)
sprintf(t2, "\"%.*s\"", minof(pllen, t2len), p);
else if (type==6) {
ss = p+xdn_expand(abuf, abuf+alen, p, t2, t2len-1);
j = strlen(t2);
t2[j++] = ' ';
ss += xdn_expand(abuf, abuf+alen, ss, t2+j, t2len-j);
j += strlen(t2+j);
snprintf(t2+j, t2len-j, "(\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)", (unsigned)peek_be(ss, 4),
(unsigned)peek_be(ss+4, 4), (unsigned)peek_be(ss+8, 4),
(unsigned)peek_be(ss+12, 4), (unsigned)peek_be(ss+16, 4));
} else if (type==15) {
j = peek_be(p, 2);
j = sprintf(t2, verbose ? "%d " : "(pri=%d) by ", j);
xdn_expand(abuf, abuf+alen, p+2, t2+j, t2len-j);
} else if (type==33) {
j = sprintf(t2, "%u %u %u ", (int)peek_be(p, 2), (int)peek_be(p+2, 2),
(int)peek_be(p+4, 2));
xdn_expand(abuf, abuf+alen, p+6, t2+j, t2len-j);
} else {
printf("%s unsupported RR type %u\n", toybuf, type);
continue;
}
for (i = 0; rrt[i].type != type; i++);
if (verbose) printf("%s\t%u\tIN %s\t%s\n", toybuf, ttl, rrt[i].name, t2);
else printf("%s %s %s\n", toybuf, rrt[i].msg, t2);
qlen++;
}
}
if (TT.t && !qlen) printf("%s has no %s record\n", *toys.optargs, TT.t);
if (CFG_TOYBOX_FREE) free(abuf);
toys.exitval = rcode;
}
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