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resolved: advertise smaller UDP datagram size on extra stubs

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This commit is contained in:
Lennart Poettering 2020-10-28 09:57:46 +01:00
parent 8facd1ce4f
commit b370adb593
1 changed files with 17 additions and 4 deletions
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21
src/resolve/resolved-dns-stub.c
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@ -15,6 +15,9 @@
* IP and UDP header sizes */
#define ADVERTISE_DATAGRAM_SIZE_MAX (65536U-14U-20U-8U)
/* On the extra stubs, use a more conservative choice */
#define ADVERTISE_EXTRA_DATAGRAM_SIZE_MAX DNS_PACKET_UNICAST_SIZE_LARGE_MAX
static int manager_dns_stub_fd_extra(Manager *m, DnsStubListenerExtra *l, int type);
static void dns_stub_listener_extra_hash_func(const DnsStubListenerExtra *a, struct siphash *state) {
@ -155,14 +158,15 @@ static int dns_stub_finish_reply_packet(
bool tc, /* set the Truncated bit? */
bool add_opt, /* add an OPT RR to this packet? */
bool edns0_do, /* set the EDNS0 DNSSEC OK bit? */
bool ad) { /* set the DNSSEC authenticated data bit? */
bool ad, /* set the DNSSEC authenticated data bit? */
uint16_t max_udp_size) { /* The maximum UDP datagram size to advertise to clients */
int r;
assert(p);
if (add_opt) {
r = dns_packet_append_opt(p, ADVERTISE_DATAGRAM_SIZE_MAX, edns0_do, /* include_rfc6975 = */ false, rcode, NULL);
r = dns_packet_append_opt(p, max_udp_size, edns0_do, /* include_rfc6975 = */ false, rcode, NULL);
if (r == -EMSGSIZE) /* Hit the size limit? then indicate truncation */
tc = true;
else if (r < 0)
@ -245,7 +249,15 @@ static int dns_stub_send_failure(
if (r < 0)
return log_debug_errno(r, "Failed to make failure packet: %m");
r = dns_stub_finish_reply_packet(reply, DNS_PACKET_ID(p), rcode, false, !!p->opt, DNS_PACKET_DO(p), authenticated);
r = dns_stub_finish_reply_packet(
reply,
DNS_PACKET_ID(p),
rcode,
/* truncated = */ false,
!!p->opt,
DNS_PACKET_DO(p),
authenticated,
l ? ADVERTISE_EXTRA_DATAGRAM_SIZE_MAX : ADVERTISE_DATAGRAM_SIZE_MAX);
if (r < 0)
return log_debug_errno(r, "Failed to build failure packet: %m");
@ -290,7 +302,8 @@ static void dns_stub_query_complete(DnsQuery *q) {
truncated,
!!q->request_dns_packet->opt,
DNS_PACKET_DO(q->request_dns_packet),
dns_query_fully_authenticated(q));
dns_query_fully_authenticated(q),
q->stub_listener_extra ? ADVERTISE_EXTRA_DATAGRAM_SIZE_MAX : ADVERTISE_DATAGRAM_SIZE_MAX);
if (r < 0) {
log_debug_errno(r, "Failed to finish reply packet: %m");
break;