197 lines
6.4 KiB
C
197 lines
6.4 KiB
C
/* host.c - DNS lookup utility
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*
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* Copyright 2014 Rich Felker <dalias@aerifal.cx>
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*
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* No standard, but there's a version in bind9
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* See https://www.ietf.org/rfc/rfc1035.txt
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* See https://www.ietf.org/rfc/rfc3596.txt
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USE_HOST(NEWTOY(host, "<1>2avt:", TOYFLAG_USR|TOYFLAG_BIN))
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config HOST
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bool "host"
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default y
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help
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usage: host [-v] [-t TYPE] NAME [SERVER]
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Look up DNS records for NAME, either domain name or IPv4/IPv6 address to
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reverse lookup, from SERVER or default DNS server(s).
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-a All records
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-t TYPE Record TYPE (number or ANY A AAAA CNAME MX NS PTR SOA SRV TXT)
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-v Verbose
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*/
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#define FOR_host
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#include "toys.h"
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#include <resolv.h>
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GLOBALS(
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char *t;
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char **nsname;
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unsigned nslen;
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)
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static const struct rrt {
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char *name, *msg;
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int type;
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} rrt[] = { { "A", "has address", 1 }, { "NS", "name server", 2 },
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{ "CNAME", "is a nickname for", 5 }, { "SOA", "start of authority", 6 },
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{ "PTR", "domain name pointer", 12 }, { "MX", "mail is handled", 15 },
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{ "TXT", "descriptive text", 16 }, { "AAAA", "has address", 28 },
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{ "SRV", "mail is handled", 33 }
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};
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int xdn_expand(char *packet, char *endpkt, char *comp, char *expand, int elen)
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{
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int i = dn_expand(packet, endpkt, comp, expand, elen);
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if (i<1) error_exit("bad dn_expand");
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return i;
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}
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// Fetch "nameserve" lines from /etc/resolv.conf. Ignores 'options' lines
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static void get_nsname(char **pline, long len)
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{
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char *line, *p;
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if (!len) return;
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line = *pline;
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if (strstart(&line, "nameserver") && isspace(*line)) {
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while (isspace(*line)) line++;
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for (p = line; *p && !isspace(*p) && *p!='#'; p++);
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if (p == line) return;
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*p = 0;
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if (!(TT.nslen&8))
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TT.nsname = xrealloc(TT.nsname, (TT.nslen+8)*sizeof(void *));
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TT.nsname[TT.nslen++] = xstrdup(line);
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}
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}
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void host_main(void)
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{
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int verbose = FLAG(a)||FLAG(v), type, abuf_len = 65536, //Largest TCP response
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i, j, sec, rcode, qlen, alen QUIET, pllen = 0, t2len = 2048;
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unsigned count, ttl;
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char *abuf = xmalloc(abuf_len), *name = *toys.optargs, *p, *ss,
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*t2 = toybuf+t2len;
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struct addrinfo *ai;
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// What kind of query are we doing?
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if (!TT.t && FLAG(a)) TT.t = "255";
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if (!getaddrinfo(name, 0,&(struct addrinfo){.ai_flags=AI_NUMERICHOST}, &ai)) {
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name = toybuf;
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if (ai->ai_family == AF_INET) {
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p = (void *)&((struct sockaddr_in *)ai->ai_addr)->sin_addr;
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sprintf(name, "%d.%d.%d.%d.in-addr.arpa", p[3], p[2], p[1], p[0]);
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} else if (ai->ai_family == AF_INET6) {
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p = (void *)&((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr;
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for (j = 0, i = 15; i>=0; i--)
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j += sprintf(name+j, "%x.%x.", p[i]&15, p[i]>>4);
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strcpy(name+j, "ip6.arpa");
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}
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if (!TT.t) TT.t = "12";
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} else if (!TT.t) TT.t = "1";
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// Prepare query packet of appropriate type
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if (TT.t[0]-'0'<10) type = atoi(TT.t); // TODO
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else if (!strcasecmp(TT.t, "any") || strcmp(TT.t, "*")) type = 255;
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else {
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for (i = 0; i<ARRAY_LEN(rrt); i++) if (!strcasecmp(TT.t, rrt[i].name)) {
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type = rrt[i].type;
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break;
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}
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if (i == ARRAY_LEN(rrt)) error_exit("bad -t: %s", TT.t);
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}
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qlen = res_mkquery(0, name, 1, type, 0, 0, 0, t2, 280); //t2len);
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if (qlen<0) error_exit("bad NAME: %s", name);
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// Grab nameservers
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if (toys.optargs[1]) TT.nsname = toys.optargs+1;
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else do_lines(xopen("/etc/resolv.conf", O_RDONLY), '\n', get_nsname);
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if (!TT.nsname) error_exit("No nameservers");
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// Send one query packet to each server until we receive response
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while (*TT.nsname) {
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if (verbose) printf("Using domain server %s:\n", *TT.nsname);
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ai = xgetaddrinfo(*TT.nsname, "53", 0, SOCK_DGRAM, 0, 0);
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i = xsocket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
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xconnect(i, ai->ai_addr, ai->ai_addrlen);
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setsockopt(i, SOL_SOCKET, SO_RCVTIMEO, &(struct timeval){ .tv_sec = 5 },
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sizeof(struct timeval));
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send(i, t2, qlen, 0);
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if (16 < (alen = recv(i, abuf, abuf_len, 0))) break;
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if (!*++TT.nsname) error_exit("Host not found.");
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close(i);
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}
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// Did it error?
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rcode = abuf[3]&7;
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if (verbose) {
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printf("rcode = %d, ancount = %d\n", rcode, (int)peek_be(abuf+6, 2));
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if (!(abuf[2]&4)) puts("The following answer is not authoritative:");
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}
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if (rcode) error_exit("Host not found: %s",
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(char *[]){ "Format error", "Server failure",
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"Non-existant domain", "Not implemented", "Refused", ""}[rcode-1]);
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// Print the result
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p = abuf + 12;
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for (sec = 0; sec<(2<<verbose); sec++) {
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count = peek_be(abuf+4+2*sec, 2);
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if (verbose && count>0 && sec>1)
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puts(sec==2 ? "For authoritative answers, see:"
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: "Additional information:");
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for (; count--; p += pllen) {
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p += xdn_expand(abuf, abuf+alen, p, toybuf, 4096-t2len);
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if (alen-(p-abuf)<10) error_exit("tilt");
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type = peek_be(p, 2);
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p += 4;
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if (!sec) continue;
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ttl = peek_be(p, 4);
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p += 4;
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pllen = peek_be(p, 2);
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p += 2;
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if ((p-abuf)+pllen>alen) error_exit("tilt");
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if (type==1 || type == 28)
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inet_ntop(type==1 ? AF_INET : AF_INET6, p, t2, t2len);
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else if (type==2 || type==5) xdn_expand(abuf, abuf+alen, p, t2, t2len);
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else if (type==16) sprintf(t2, "\"%.*s\"", minof(pllen, t2len), p);
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else if (type==6) {
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ss = p+xdn_expand(abuf, abuf+alen, p, t2, t2len-1);
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j = strlen(t2);
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t2[j++] = ' ';
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ss += xdn_expand(abuf, abuf+alen, ss, t2+j, t2len-j);
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j += strlen(t2+j);
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snprintf(t2+j, t2len-j, "(\n\t\t%u\t;serial (version)\n\t\t%u\t"
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";refresh period\n\t\t%u\t;retry interval\n\t\t%u\t;expire time\n"
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"\t\t%u\t;default ttl\n\t\t)", (unsigned)peek_be(ss, 4),
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(unsigned)peek_be(ss+4, 4), (unsigned)peek_be(ss+8, 4),
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(unsigned)peek_be(ss+12, 4), (unsigned)peek_be(ss+16, 4));
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} else if (type==15) {
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j = peek_be(p, 2);
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j = sprintf(t2, verbose ? "%d " : "(pri=%d) by ", j);
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xdn_expand(abuf, abuf+alen, p+2, t2+j, t2len-j);
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} else if (type==33) {
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j = sprintf(t2, "%u %u %u ", (int)peek_be(p, 2), (int)peek_be(p+2, 2),
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(int)peek_be(p+4, 2));
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xdn_expand(abuf, abuf+alen, p+6, t2+j, t2len-j);
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} else {
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printf("%s unsupported RR type %u\n", toybuf, type);
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continue;
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}
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for (i = 0; rrt[i].type != type; i++);
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if (verbose) printf("%s\t%u\tIN %s\t%s\n", toybuf, ttl, rrt[i].name, t2);
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else printf("%s %s %s\n", toybuf, rrt[type].msg, t2);
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}
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}
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if (CFG_TOYBOX_FREE) free(abuf);
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toys.exitval = rcode;
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}
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