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MINOR: dns: enabled edns0 extension and make accpeted payload size tunable

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Edns extensions may be used to negotiate some settings between a DNS
client and a server.
For now we only use it to announce the maximum response payload size accpeted
by HAProxy.
This size can be set through a configuration parameter in the resolvers
section. If not set, it defaults to 512 bytes.
This commit is contained in:
Baptiste Assmann
2017-08-14 00:13:01 +02:00
committed by Willy Tarreau
parent 572ab8b269
commit 2af08fe3de
5 changed files with 54 additions and 5 deletions
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2
include/proto/dns.h
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@@ -29,7 +29,7 @@ char *dns_str_to_dn_label(const char *string, char *dn, int dn_len);
int dns_str_to_dn_label_len(const char *string);
void dns_dn_label_to_str(char *dn, char *str, int dn_len);
int dns_hostname_validation(const char *string, char **err);
int dns_build_query(int query_id, int query_type, char *hostname_dn, int hostname_dn_len, char *buf, int bufsize);
int dns_build_query(int query_id, int query_type, unsigned int accepted_payload_size, char *hostname_dn, int hostname_dn_len, char *buf, int bufsize);
struct task *dns_process_resolve(struct task *t);
int dns_init_resolvers(int close_socket);
uint16_t dns_rnd16(void);

15
include/types/dns.h
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@@ -112,6 +112,20 @@ struct dns_query_item {
unsigned short class; /* query class */
};
/* NOTE: big endian structure */
struct dns_additional_record {
uint8_t name; /* domain name, must be 0 (RFC 6891) */
uint16_t type; /* record type DNS_RTYPE_OPT (41) */
uint16_t udp_payload_size; /* maximum size accepted for the response */
uint32_t extension; /* extended rcode and flags, not used for now */
uint16_t data_length; /* data length */
/* as of today, we don't support yet edns options, that said I already put a placeholder here
* for this purpose. We may need to define a dns_option_record structure which itself should
* point to different type of data, based on the extension set (client subnet, tcp keepalive,
* etc...)*/
// struct list options; /* list of option records */
} __attribute__ ((packed));
/* NOTE: big endian structure */
struct dns_answer_item {
struct list list;
@@ -150,6 +164,7 @@ struct dns_resolvers {
int line; /* line where the section appears */
} conf; /* config information */
struct list nameserver_list; /* dns server list */
unsigned int accepted_payload_size; /* maximum payload size we accept for responses */
int count_nameservers; /* total number of nameservers in a resolvers section */
int resolve_retries; /* number of retries before giving up */
struct { /* time to: */