diff options
| -rw-r--r-- | getservinfo.c | 92 |
1 files changed, 34 insertions, 58 deletions
diff --git a/getservinfo.c b/getservinfo.c index 04685d7..219f72a 100644 --- a/getservinfo.c +++ b/getservinfo.c @@ -41,35 +41,12 @@ #define EAI_PROTOCOL EAI_BADFLAGS #endif -static uint16_t u16(uint8_t **ptr) { - uint16_t x = *(*ptr)++; - x = x << 8 | *(*ptr)++; - return x; -} - -static void nameSkip(uint8_t **ptr) { - for (uint8_t len; (len = *(*ptr)++); *ptr += len) { - if (len & 0xC0) { - (*ptr)++; - break; - } - } -} - -static char *nameString(uint8_t **ptr) { - char *name = (char *)*ptr; - if (**ptr) name++; - for (uint8_t len; (len = **ptr); *ptr += len) { - *(*ptr)++ = '.'; - } - return name; -} - /* A wrapper around getaddrinfo(3) which first performs SRV record (RFC 2782) * lookup. hints must be provided and hints->ai_protocol must be set. SRV * lookup is skipped if servname is numerical. If SRV lookup is successful, the * ai_canonname field of the first addrinfo structure returned is set to the - * target name. + * target name. Only the first SRV record is used. Priority and weight are + * ignored. */ int getservinfo( const char *hostname, const char *servname, @@ -77,12 +54,12 @@ int getservinfo( ) { if (!hints) return EAI_BADHINTS; if (!hints->ai_protocol) return EAI_PROTOCOL; - if (hints->ai_flags & AI_NUMERICHOST) return EAI_BADFLAGS; - if (hints->ai_flags & AI_NUMERICSERV) return EAI_BADFLAGS; char *rest; strtoul(servname, &rest, 10); - if (!*rest) return getaddrinfo(hostname, servname, hints, res); + if (!*rest || hints->ai_flags & (AI_NUMERICHOST | AI_NUMERICSERV)) { + return getaddrinfo(hostname, servname, hints, res); + } struct protoent *proto = getprotobynumber(hints->ai_protocol); if (!proto) return EAI_PROTOCOL; @@ -96,45 +73,44 @@ int getservinfo( uint8_t msg[512]; len = res_query(dname, 1 /* IN */, 33 /* SRV */, msg, sizeof(msg)); - if (len < 0) return getaddrinfo(hostname, servname, hints, res); - - uint8_t *ptr = msg; - u16(&ptr); // ID - u16(&ptr); // QR, OPCODE, AA, TC, RD, RA, Z, RCODE - uint16_t qdcount = u16(&ptr); - u16(&ptr); // ANCOUNT - u16(&ptr); // NSCOUNT - u16(&ptr); // ARCOUNT + if (len < 12) return getaddrinfo(hostname, servname, hints, res); + uint8_t *ptr = &msg[12]; + +#define NAME_SKIP \ + for (uint8_t n; ptr < &msg[len] && (n = *ptr++); ptr += n) { \ + if (n & 0xC0) { \ + ptr++; \ + break; \ + } \ + } - for (uint16_t q = 0; q < qdcount; ++q) { - nameSkip(&ptr); // QNAME - u16(&ptr); // QTYPE - u16(&ptr); // QCLASS + uint16_t qdcount = msg[4] << 8 | msg[5]; + for (uint16_t q = 0; ptr < &msg[len] && q < qdcount; ++q) { + NAME_SKIP; // QNAME + ptr += 4; // QTYPE, QCLASS } - // Read only one answer, ignoring Priority and Weight. Does anyone actually - // use them? - nameSkip(&ptr); // NAME - u16(&ptr); // TYPE - u16(&ptr); // CLASS - u16(&ptr); // TTL - u16(&ptr); // TTL - u16(&ptr); // RDLENGTH - u16(&ptr); // Priority - u16(&ptr); // Weight + NAME_SKIP; // NAME + ptr += 14; // TYPE, CLASS, TTL, RDLENGTH, Priority, Weight + if (&msg[len] < ptr + 3) { + return getaddrinfo(hostname, servname, hints, res); + } - uint16_t port = u16(&ptr); - hostname = nameString(&ptr); - if (!hostname[0]) return EAI_NONAME; + char port[sizeof("65535")]; + snprintf(port, sizeof(port), "%d", ptr[0] << 8 | ptr[1]); + ptr += 2; - char myServ[sizeof("65535")]; - snprintf(myServ, sizeof(myServ), "%hu", port); + // Name compression is not used for Target. + if (!ptr[0]) return EAI_NONAME; + hostname = (const char *)&ptr[1]; + for (uint8_t n; ptr < &msg[len] && (n = *ptr); ptr += n) { + *ptr++ = '.'; + } struct addrinfo myHints = *hints; myHints.ai_flags |= AI_NUMERICSERV; myHints.ai_flags &= ~AI_CANONNAME; - - int error = getaddrinfo(hostname, myServ, &myHints, res); + int error = getaddrinfo(hostname, port, &myHints, res); if (error) return error; (*res)->ai_canonname = strdup(hostname); |