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resolved: set the DNSSEC OK (DO) flag

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This indicates that we can handle DNSSEC records (per RFC3225), even if
all we do is silently drop them. This feature requires EDNS0 support.

As we do not yet support larger UDP packets, this feature increases the
risk of getting truncated packets.

Similarly to how we fall back to plain UDP if EDNS0 fails, we will fall
back to plain EDNS0 if EDNS0+DO fails (with the same logic of remembering
success and retrying after a grace period after failure).
This commit is contained in:
Tom Gundersen 2015-06-24 15:08:40 +02:00
parent 9c5e12a431
commit 7586f4d172
5 changed files with 13 additions and 5 deletions
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8
src/resolve/resolved-dns-packet.c
View File

@ -28,6 +28,8 @@
#include "utf8.h"
#include "util.h"
#define EDNS0_OPT_DO (1<<15)
int dns_packet_new(DnsPacket **ret, DnsProtocol protocol, size_t mtu) {
DnsPacket *p;
size_t a;
@ -610,7 +612,7 @@ fail:
}
/* Append the OPT pseudo-RR described in RFC6891 */
int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, size_t *start) {
int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start) {
size_t saved_size;
int r;
@ -640,8 +642,8 @@ int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, size_t *start)
if (r < 0)
goto fail;
/* flags */
r = dns_packet_append_uint16(p, 0, NULL);
/* flags: DNSSEC OK (DO), see RFC3225 */
r = dns_packet_append_uint16(p, edns0_do ? EDNS0_OPT_DO : 0, NULL);
if (r < 0)
goto fail;

2
src/resolve/resolved-dns-packet.h
View File

@ -160,7 +160,7 @@ int dns_packet_append_label(DnsPacket *p, const char *s, size_t l, size_t *start
int dns_packet_append_name(DnsPacket *p, const char *name, bool allow_compression, size_t *start);
int dns_packet_append_key(DnsPacket *p, const DnsResourceKey *key, size_t *start);
int dns_packet_append_rr(DnsPacket *p, const DnsResourceRecord *rr, size_t *start);
int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, size_t *start);
int dns_packet_append_opt_rr(DnsPacket *p, uint16_t max_udp_size, bool edns0_do, size_t *start);
void dns_packet_truncate(DnsPacket *p, size_t sz);

6
src/resolve/resolved-dns-scope.c
View File

@ -185,7 +185,11 @@ int dns_scope_emit(DnsScope *s, int fd, DnsServer *server, DnsPacket *p) {
return -EOPNOTSUPP;
if (server->possible_features >= DNS_SERVER_FEATURE_LEVEL_EDNS0) {
r = dns_packet_append_opt_rr(p, DNS_PACKET_UNICAST_SIZE_MAX, &saved_size);
bool edns_do;
edns_do = server->possible_features >= DNS_SERVER_FEATURE_LEVEL_DO;
r = dns_packet_append_opt_rr(p, DNS_PACKET_UNICAST_SIZE_MAX, edns_do, &saved_size);
if (r < 0)
return r;

1
src/resolve/resolved-dns-server.c
View File

@ -479,5 +479,6 @@ static const char* const dns_server_feature_level_table[_DNS_SERVER_FEATURE_LEVE
[DNS_SERVER_FEATURE_LEVEL_TCP] = "TCP",
[DNS_SERVER_FEATURE_LEVEL_UDP] = "UDP",
[DNS_SERVER_FEATURE_LEVEL_EDNS0] = "UDP+EDNS0",
[DNS_SERVER_FEATURE_LEVEL_DO] = "UDP+EDNS0+DO",
};
DEFINE_STRING_TABLE_LOOKUP(dns_server_feature_level, DnsServerFeatureLevel);

1
src/resolve/resolved-dns-server.h
View File

@ -35,6 +35,7 @@ typedef enum DnsServerFeatureLevel {
DNS_SERVER_FEATURE_LEVEL_TCP,
DNS_SERVER_FEATURE_LEVEL_UDP,
DNS_SERVER_FEATURE_LEVEL_EDNS0,
DNS_SERVER_FEATURE_LEVEL_DO,
_DNS_SERVER_FEATURE_LEVEL_MAX,
_DNS_SERVER_FEATURE_LEVEL_INVALID = -1
} DnsServerFeatureLevel;