diff options
Diffstat (limited to 'src/network/__dns.c')
| -rw-r--r-- | src/network/__dns.c | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/src/network/__dns.c b/src/network/__dns.c new file mode 100644 index 00000000..73ec422d --- /dev/null +++ b/src/network/__dns.c @@ -0,0 +1,267 @@ +#include <stdint.h> +#include <netdb.h> +#include <stdio.h> +#include <fcntl.h> +#include <limits.h> +#include <string.h> +#include <sys/socket.h> +#include <sys/select.h> +#include <sys/time.h> +#include <netinet/in.h> +#include <time.h> +#include <ctype.h> +#include <unistd.h> +#include "__dns.h" +#include "stdio_impl.h" + +#define TIMEOUT 5 +#define RETRY 1 +#define PACKET_MAX 512 +#define PTR_MAX (64 + sizeof ".in-addr.arpa") + +int __dns_doqueries(unsigned char *dest, const char *name, int *rr, int rrcnt) +{ + time_t t0 = time(0); + int fd; + FILE *f, _f; + unsigned char _buf[64]; + char line[64], *s, *z; + union { + struct sockaddr_in sin; + struct sockaddr_in6 sin6; + } sa = {0}, ns[3] = {{0}}; + socklen_t sl; + int nns; + int family; + unsigned char q[280] = "", *r = dest; + int ql; + int rlen; + int got = 0, failed = 0; + int errcode = EAI_AGAIN; + int i, j; + struct timeval tv; + fd_set fds; + int id; + + /* Construct query template - RR and ID will be filled later */ + if (strlen(name)-1 >= 254U) return -1; + q[2] = q[5] = 1; + strcpy(q+13, name); + for (i=13; q[i]; i=j+1) { + for (j=i; q[j] && q[j] != '.'; j++); + if (j-i-1u > 62u) return -1; + q[i-1] = j-i; + } + q[i+3] = 1; + ql = i+4; + + /* Make a reasonably unpredictable id */ + gettimeofday(&tv, 0); + id = tv.tv_usec + tv.tv_usec/256 & 0xffff; + + /* Get nameservers from resolv.conf, fallback to localhost */ + f = __fopen_rb_ca("/etc/resolv.conf", &_f, _buf, sizeof _buf); + if (f) for (nns=0; nns<3 && fgets(line, sizeof line, f); ) { + if (strncmp(line, "nameserver", 10) || !isspace(line[10])) + continue; + for (s=line+11; isspace(*s); s++); + for (z=s; *z && !isspace(*z); z++); + *z=0; + if (__ipparse(ns+nns, family, s) < 0) continue; + ns[nns].sin.sin_port = htons(53); + family = ns[nns++].sin.sin_family; + sl = family==AF_INET6 ? sizeof sa.sin6 : sizeof sa.sin; + } + if (f) __fclose_ca(f); + if (!nns) { + ns[0].sin.sin_family = AF_INET; + ns[0].sin.sin_port = htons(53); + nns=1; + sl = sizeof sa.sin; + } + + /* Get local address and open/bind a socket */ + sa.sin.sin_family = family; + fd = socket(family, SOCK_DGRAM, 0); + if (bind(fd, (void *)&sa, sl) < 0) { + close(fd); + return -1; + } + /* Nonblocking to work around Linux UDP select bug */ + fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK); + + /* Loop until we timeout; break early on success */ + for (; time(0)-t0 < TIMEOUT; ) { + + /* Query all configured namservers in parallel */ + for (i=0; i<rrcnt; i++) if (rr[i]) for (j=0; j<nns; j++) { + q[0] = id+i >> 8; + q[1] = id+i; + q[ql-3] = rr[i]; + sendto(fd, q, ql, MSG_NOSIGNAL, (void *)&ns[j], sl); + } + + /* Wait for a response, or until time to retry */ + FD_ZERO(&fds); + FD_SET(fd, &fds); + tv.tv_sec = RETRY; + tv.tv_usec = 0; + if (select(fd+1, &fds, 0, 0, &tv) <= 0) continue; + + /* Process any and all replies */ + while (got+failed < rrcnt && (rlen = recvfrom(fd, r, 512, 0, + (void *)&sa, (socklen_t[1]){sl})) >= 2) + { + /* Ignore replies from addresses we didn't send to */ + for (i=0; i<nns; i++) if (!memcmp(ns+i, &sa, sl)) break; + if (i==nns) continue; + + /* Compute index of the query from id */ + i = r[0]*256+r[1] - id & 0xffff; + if ((unsigned)i >= rrcnt || !rr[i]) continue; + + /* Interpret the result code */ + switch (r[3] & 15) { + case 0: + got++; + break; + case 3: + if (1) errcode = EAI_NONAME; else + default: + errcode = EAI_FAIL; + failed++; + } + + /* Mark this record as answered */ + rr[i] = 0; + r += 512; + } + + /* Check to see if we have answers to all queries */ + if (got+failed == rrcnt) break; + } + close(fd); + + /* Return the number of results, or an error code if none */ + if (got) return got; + return errcode; +} + +static void mkptr4(char *s, const unsigned char *ip) +{ + sprintf(s, "%d.%d.%d.%d.in-addr.arpa", + ip[3], ip[2], ip[1], ip[0]); +} + +static void mkptr6(char *s, const unsigned char *ip) +{ + static const char xdigits[] = "0123456789abcdef"; + int i; + for (i=15; i>=0; i--) { + *s++ = xdigits[ip[i]&15]; *s++ = '.'; + *s++ = xdigits[ip[i]>>4]; *s++ = '.'; + } + strcpy(s, "ip6.arpa"); +} + +int __dns_query(unsigned char *r, const void *a, int family, int ptr) +{ + char buf[PTR_MAX]; + int rr[2], rrcnt = 1; + + if (ptr) { + if (family == AF_INET6) mkptr6(buf, a); + else mkptr4(buf, a); + rr[0] = RR_PTR; + a = buf; + } else if (family == AF_INET6) { + rr[0] = RR_AAAA; + } else { + rr[0] = RR_A; + if (family != AF_INET) rr[rrcnt++] = RR_AAAA; + } + + return __dns_doqueries(r, a, rr, rrcnt); +} + + +#define BITOP(a,b,op) \ + ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a)))) + +static int decname(char *s, const unsigned char *b, const unsigned char *p) +{ + /* Remember jump destinations to detect loops and abort */ + size_t seen[PACKET_MAX/8/sizeof(size_t)] = { 0 }; + char *sz = s + HOST_NAME_MAX; + const unsigned char *pz = b+512; + for (;;) { + if (p>=pz) return -1; + else if (*p&0xc0) { + int j = (p[0]&1) | p[1]; + if (BITOP(seen, j, &)) return -1; + BITOP(seen, j, |=); + p = b + j; + } else if (*p) { + if (p+*p+1>=pz || s+*p>=sz) return -1; + memcpy(s, p+1, *p); + s += *p+1; + p += *p+1; + s[-1] = *p ? '.' : 0; + } else return 0; + } +} + +int __dns_get_rr(void *dest, size_t stride, size_t maxlen, size_t limit, const unsigned char *r, int rr, int dec) +{ + int qdcount, ancount; + const unsigned char *p; + char tmp[256]; + int found = 0; + int len; + + if ((r[3]&15)) return 0; + p = r+12; + qdcount = r[4]*256 + r[5]; + ancount = r[6]*256 + r[7]; + if (qdcount+ancount > 64) return -1; + while (qdcount--) { + while (p-r < 512 && *p-1U < 127) p++; + if (*p>193 || (*p==193 && p[1]>254) || p>r+506) + return -1; + p += 5 + !!*p; + } + while (ancount--) { + while (p-r < 512 && *p-1U < 127) p++; + if (*p>193 || (*p==193 && p[1]>254) || p>r+506) + return -1; + p += 1 + !!*p; + len = p[8]*256 + p[9]; + if (p+len > r+512) return -1; + if (p[1]==rr && len <= maxlen) { + if (dec && decname(tmp, r, p+10)<0) return -1; + if (dest && limit) { + if (dec) strcpy(dest, tmp); + else memcpy(dest, p+10, len); + dest = (char *)dest + stride; + limit--; + } + found++; + } + p += 10 + len; + } + return found; +} + +int __dns_count_addrs(const unsigned char *r, int cnt) +{ + int found=0, res, i; + static const int p[2][2] = { { 4, RR_A }, { 16, RR_AAAA } }; + + while (cnt--) for (i=0; i<2; i++) { + res = __dns_get_rr(0, 0, p[i][0], -1, r, p[i][1], 0); + if (res < 0) return res; + found += res; + r += 512; + } + return found; +} |