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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 }, { "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;
- 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==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[type].msg, t2);
- }
- }
- if (CFG_TOYBOX_FREE) free(abuf);
- toys.exitval = rcode;
- }
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