Macros
#define	N_DNS_QNAME_MAX 256
	Maximum decoded QNAME length, including the terminating NUL.

#define	N_DNS_TYPE_A 1
	DNS resource-record type A (IPv4 address).

Functions
int	n_dns_build_a_response (const unsigned char query, size_t qlen, uint32_t ipv4_be, uint32_t ttl, unsigned char out, size_t outsz)
	Build a DNS response answering a query's first question with one A record.

int	n_dns_parse_query (const unsigned char msg, size_t len, uint16_t id_out, char qname_out, size_t qname_sz, uint16_t qtype_out)
	Parse the header id and the first question (QNAME + QTYPE) of a DNS message.

Detailed Description

Macro Definition Documentation

◆ N_DNS_QNAME_MAX

#define N_DNS_QNAME_MAX 256

Maximum decoded QNAME length, including the terminating NUL.

Examples: ex_dns.c.

Definition at line 43 of file n_dns.h.

◆ N_DNS_TYPE_A

#define N_DNS_TYPE_A 1

DNS resource-record type A (IPv4 address).

Examples: ex_dns.c.

Definition at line 45 of file n_dns.h.

Function Documentation

◆ n_dns_build_a_response()

int n_dns_build_a_response	(	const unsigned char *	query,
		size_t	qlen,
		uint32_t	ipv4_be,
		uint32_t	ttl,
		unsigned char *	out,
		size_t	outsz
	)

Build a DNS response answering a query's first question with one A record.

Echoes the query header (with QR/AA/RA set and RCODE 0) and question, then appends a single A resource record pointing at ipv4_be. The address is taken in network byte order (as returned by inet_addr) and copied verbatim into the RDATA, so the helper is endianness-agnostic.

Parameters

query	The received query bytes. NULL returns -1.
qlen	The query length in bytes.
ipv4_be	The answer IPv4 address, in network byte order.
ttl	The record time-to-live in seconds.
out	Output buffer for the response. NULL returns -1.
outsz	Size of `out`.

Returns: The response length in bytes, or -1 on a malformed query or too-small buffer.

Definition at line 94 of file n_dns.c.

References N_DNS_HEADER_LEN, and n_dns_u16().

Referenced by test_build_response(), and test_errors().

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◆ n_dns_parse_query()

int n_dns_parse_query	(	const unsigned char *	msg,
		size_t	len,
		uint16_t *	id_out,
		char *	qname_out,
		size_t	qname_sz,
		uint16_t *	qtype_out
	)

Parse the header id and the first question (QNAME + QTYPE) of a DNS message.

The QNAME is written as a lowercase dot-separated string (no trailing dot). Name compression is rejected in the question (a query has none). Any out pointer may be NULL to skip it.