diff options
Diffstat (limited to 'include/arpa/nameser.h')
-rw-r--r-- | include/arpa/nameser.h | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/include/arpa/nameser.h b/include/arpa/nameser.h index 6e4808f00d..c27e7886b7 100644 --- a/include/arpa/nameser.h +++ b/include/arpa/nameser.h @@ -103,5 +103,97 @@ libc_hidden_proto (__libc_ns_samename) must point one past the last byte in the packet. */ int __ns_name_length_uncompressed (const unsigned char *p, const unsigned char *eom) attribute_hidden; + +/* Iterator over the resource records in a DNS packet. */ +struct ns_rr_cursor +{ + /* These members are not changed after initialization. */ + const unsigned char *begin; /* First byte of packet. */ + const unsigned char *end; /* One past the last byte of the packet. */ + const unsigned char *first_rr; /* First resource record (or packet end). */ + + /* Advanced towards the end while reading the packet. */ + const unsigned char *current; +}; + +/* Returns the RCODE field from the DNS header. */ +static inline int +ns_rr_cursor_rcode (const struct ns_rr_cursor *c) +{ + return c->begin[3] & 0x0f; /* Lower 4 bits at offset 3. */ +} + +/* Returns the length of the answer section according to the DNS header. */ +static inline int +ns_rr_cursor_ancount (const struct ns_rr_cursor *c) +{ + return c->begin[6] * 256 + c->begin[7]; /* 16 bits at offset 6. */ +} + +/* Returns the length of the authority (name server) section according + to the DNS header. */ +static inline int +ns_rr_cursor_nscount (const struct ns_rr_cursor *c) +{ + return c->begin[8] * 256 + c->begin[9]; /* 16 bits at offset 8. */ +} + +/* Returns the length of the additional data section according to the + DNS header. */ +static inline int +ns_rr_cursor_adcount (const struct ns_rr_cursor *c) +{ + return c->begin[10] * 256 + c->begin[11]; /* 16 bits at offset 10. */ +} + +/* Returns a pointer to the uncompressed question name in wire + format. */ +static inline const unsigned char * +ns_rr_cursor_qname (const struct ns_rr_cursor *c) +{ + return c->begin + 12; /* QNAME starts right after the header. */ +} + +/* Returns the question type of the first and only question. */ +static inline const int +ns_rr_cursor_qtype (const struct ns_rr_cursor *c) +{ + /* 16 bits 4 bytes back from the first RR header start. */ + return c->first_rr[-4] * 256 + c->first_rr[-3]; +} + +/* Returns the clss of the first and only question (usally C_IN). */ +static inline const int +ns_rr_cursor_qclass (const struct ns_rr_cursor *c) +{ + /* 16 bits 2 bytes back from the first RR header start. */ + return c->first_rr[-2] * 256 + c->first_rr[-1]; +} + +/* Initializes *C to cover the packet [BUF, BUF+LEN). Returns false + if LEN is less than sizeof (*HD), if the packet does not contain a + full (uncompressed) question, or if the question count is not 1. */ +_Bool __ns_rr_cursor_init (struct ns_rr_cursor *c, + const unsigned char *buf, size_t len) + attribute_hidden; + +/* Like ns_rr, but the record owner name is not decoded into text format. */ +struct ns_rr_wire +{ + unsigned char rname[NS_MAXCDNAME]; /* Owner name of the record. */ + uint16_t rtype; /* Resource record type (T_*). */ + uint16_t rclass; /* Resource record class (C_*). */ + uint32_t ttl; /* Time-to-live field. */ + const unsigned char *rdata; /* Start of resource record data. */ + uint16_t rdlength; /* Length of the data at rdata, in bytes. */ +}; + +/* Attempts to parse the record at C into *RR. On success, return + true, and C is advanced past the record, and RR->rdata points to + the record data. On failure, errno is set to EMSGSIZE, and false + is returned. */ +_Bool __ns_rr_cursor_next (struct ns_rr_cursor *c, struct ns_rr_wire *rr) + attribute_hidden; + # endif /* !_ISOMAC */ #endif |