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Merge pull request #29927 from yuwata/resolve-mdns-fixlets

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resolve: several mdns fixlets
This commit is contained in:
Luca Boccassi
2023-11-08 19:56:31 +00:00
committed by GitHub
parent 98a10e385d dd51c4332f
commit fe7109fc2e
5 changed files with 118 additions and 95 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/resolve/resolved-dns-cache.c
+13 -12
View File
@@ -1308,6 +1308,19 @@ int dns_cache_export_shared_to_packet(DnsCache *cache, DnsPacket *p, usec_t ts,
if (usec_sub_unsigned(j->until, ts) < j->rr->ttl * USEC_PER_SEC / 2)
continue;
if (max_rr > 0 && ancount >= max_rr) {
DNS_PACKET_HEADER(p)->ancount = htobe16(ancount);
ancount = 0;
r = dns_packet_new_query(&p->more, p->protocol, 0, true);
if (r < 0)
return r;
p = p->more;
max_rr = UINT_MAX;
}
r = dns_packet_append_rr(p, j->rr, 0, NULL, NULL);
if (r == -EMSGSIZE) {
if (max_rr == 0)
@@ -1333,18 +1346,6 @@ int dns_cache_export_shared_to_packet(DnsCache *cache, DnsPacket *p, usec_t ts,
return r;
ancount++;
if (max_rr > 0 && ancount >= max_rr) {
DNS_PACKET_HEADER(p)->ancount = htobe16(ancount);
ancount = 0;
r = dns_packet_new_query(&p->more, p->protocol, 0, true);
if (r < 0)
return r;
p = p->more;
max_rr = UINT_MAX;
}
}
finalize:
src/resolve/resolved-dns-packet.c
+3 -3
View File
@@ -307,13 +307,13 @@ int dns_packet_validate_query(DnsPacket *p) {
if (DNS_PACKET_OPCODE(p) != 0)
return -EBADMSG;
if (DNS_PACKET_TC(p))
return -EBADMSG;
switch (p->protocol) {
case DNS_PROTOCOL_LLMNR:
case DNS_PROTOCOL_DNS:
if (DNS_PACKET_TC(p)) /* mDNS query may have truncation flag. */
return -EBADMSG;
/* RFC 4795, Section 2.1.1. says to discard all queries with QDCOUNT != 1 */
if (DNS_PACKET_QDCOUNT(p) != 1)
return -EBADMSG;
src/resolve/resolved-dns-transaction.c
+96 -78
View File
@@ -1786,21 +1786,20 @@ static int dns_packet_append_zone(DnsPacket *p, DnsTransaction *t, DnsResourceKe
return dns_packet_append_answer(p, answer, nscount);
}
static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
static int mdns_make_dummy_packet(DnsTransaction *t, DnsPacket **ret_packet, Set **ret_keys) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
_cleanup_set_free_ Set *keys = NULL;
unsigned qdcount, ancount = 0 /* avoid false maybe-uninitialized warning */, nscount;
bool add_known_answers = false;
unsigned qdcount;
usec_t ts;
int r;
assert(t);
assert(t->scope);
assert(t->scope->protocol == DNS_PROTOCOL_MDNS);
assert(ret_packet);
assert(ret_keys);
/* Discard any previously prepared packet, so we can start over and coalesce again */
t->sent = dns_packet_unref(t->sent);
/* First, create a dummy packet to calculate packet size. */
r = dns_packet_new_query(&p, t->scope->protocol, 0, false);
if (r < 0)
return r;
@@ -1823,120 +1822,139 @@ static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
if (r < 0)
return r;
/*
* For mDNS, we want to coalesce as many open queries in pending transactions into one single
* query packet on the wire as possible. To achieve that, we iterate through all pending transactions
* in our current scope, and see whether their timing constraints allow them to be sent.
*/
assert_se(sd_event_now(t->scope->manager->event, CLOCK_BOOTTIME, &ts) >= 0);
for (bool restart = true; restart;) {
restart = false;
LIST_FOREACH(transactions_by_scope, other, t->scope->transactions) {
LIST_FOREACH(transactions_by_scope, other, t->scope->transactions) {
/* Skip ourselves */
if (other == t)
continue;
if (other->state != DNS_TRANSACTION_PENDING)
continue;
if (other->next_attempt_after > ts)
continue;
if (!set_contains(keys, dns_transaction_key(other))) {
size_t saved_packet_size;
bool append = false;
/* Skip ourselves */
if (other == t)
continue;
if (other->state != DNS_TRANSACTION_PENDING)
continue;
if (other->next_attempt_after > ts)
continue;
if (!set_contains(keys, dns_transaction_key(other))) {
r = dns_packet_append_key(p, dns_transaction_key(other), 0, &saved_packet_size);
/* If we can't stuff more questions into the packet, just give up.
* One of the 'other' transactions will fire later and take care of the rest. */
if (r == -EMSGSIZE)
break;
if (r < 0)
return r;
r = dns_packet_append_zone(p, t, dns_transaction_key(other), NULL);
if (r == -EMSGSIZE)
break;
if (r < 0)
return r;
append = true;
}
r = dns_transaction_prepare(other, ts);
if (r < 0)
return r;
if (r == 0) {
if (append)
dns_packet_truncate(p, saved_packet_size);
/* In this case, not only this transaction, but multiple transactions may be
* freed. Hence, we need to restart the loop. */
restart = true;
r = dns_packet_append_key(p, dns_transaction_key(other), 0, &saved_packet_size);
/* If we can't stuff more questions into the packet, just give up.
* One of the 'other' transactions will fire later and take care of the rest. */
if (r == -EMSGSIZE)
break;
}
usec_t timeout = transaction_get_resend_timeout(other);
r = dns_transaction_setup_timeout(other, timeout, usec_add(ts, timeout));
if (r < 0)
return r;
if (dns_key_is_shared(dns_transaction_key(other)))
add_known_answers = true;
if (append) {
r = set_ensure_put(&keys, &dns_resource_key_hash_ops, dns_transaction_key(other));
if (r < 0)
return r;
}
qdcount++;
if (qdcount >= UINT16_MAX)
r = dns_packet_append_zone(p, t, dns_transaction_key(other), NULL);
if (r == -EMSGSIZE) {
dns_packet_truncate(p, saved_packet_size);
break;
}
if (r < 0)
return r;
r = set_ensure_put(&keys, &dns_resource_key_hash_ops, dns_transaction_key(other));
if (r < 0)
return r;
}
r = dns_transaction_prepare(other, ts);
if (r < 0)
return r;
if (r == 0)
/* In this case, not only this transaction, but multiple transactions may be
* freed. Hence, we need to restart the loop. */
return -EAGAIN;
usec_t timeout = transaction_get_resend_timeout(other);
r = dns_transaction_setup_timeout(other, timeout, usec_add(ts, timeout));
if (r < 0)
return r;
if (dns_key_is_shared(dns_transaction_key(other)))
add_known_answers = true;
qdcount++;
if (qdcount >= UINT16_MAX)
break;
}
/* Append known answer section if we're asking for any shared record */
DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount);
/* Append known answers section if we're asking for any shared record */
if (add_known_answers) {
r = dns_cache_export_shared_to_packet(&t->scope->cache, p, ts, 0);
if (r < 0)
return r;
}
ancount = be16toh(DNS_PACKET_HEADER(p)->ancount);
*ret_packet = TAKE_PTR(p);
*ret_keys = TAKE_PTR(keys);
return add_known_answers;
}
static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL, *dummy = NULL;
_cleanup_set_free_ Set *keys = NULL;
bool add_known_answers;
DnsResourceKey *k;
unsigned c;
int r;
assert(t);
assert(t->scope->protocol == DNS_PROTOCOL_MDNS);
/* Discard any previously prepared packet, so we can start over and coalesce again */
t->sent = dns_packet_unref(t->sent);
/* First, create a dummy packet to calculate the number of known answers to be appended in the first packet. */
for (;;) {
r = mdns_make_dummy_packet(t, &dummy, &keys);
if (r == -EAGAIN)
continue;
if (r < 0)
return r;
add_known_answers = r;
break;
}
/* Then, create actual packet. */
p = dns_packet_unref(p);
r = dns_packet_new_query(&p, t->scope->protocol, 0, false);
if (r < 0)
return r;
/* Questions */
DnsResourceKey *k;
c = 0;
SET_FOREACH(k, keys) {
r = dns_packet_append_key(p, k, 0, NULL);
if (r < 0)
return r;
c++;
}
DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount);
DNS_PACKET_HEADER(p)->qdcount = htobe16(c);
/* Known answers */
if (add_known_answers) {
r = dns_cache_export_shared_to_packet(&t->scope->cache, p, ts, ancount);
usec_t ts;
assert_se(sd_event_now(t->scope->manager->event, CLOCK_BOOTTIME, &ts) >= 0);
r = dns_cache_export_shared_to_packet(&t->scope->cache, p, ts, be16toh(DNS_PACKET_HEADER(dummy)->ancount));
if (r < 0)
return r;
}
/* Authorities */
nscount = 0;
c = 0;
SET_FOREACH(k, keys) {
r = dns_packet_append_zone(p, t, k, &nscount);
r = dns_packet_append_zone(p, t, k, &c);
if (r < 0)
return r;
}
DNS_PACKET_HEADER(p)->nscount = htobe16(nscount);
DNS_PACKET_HEADER(p)->nscount = htobe16(c);
t->sent = TAKE_PTR(p);
return 0;
src/resolve/resolved-manager.c
+4 -1
View File
@@ -1198,8 +1198,11 @@ int manager_send(
assert(port > 0);
assert(p);
/* For mDNS, it is natural that the packet have truncated flag when we have many known answers. */
bool truncated = DNS_PACKET_TC(p) && (p->protocol != DNS_PROTOCOL_MDNS || !p->more);
log_debug("Sending %s%s packet with id %" PRIu16 " on interface %i/%s of size %zu.",
DNS_PACKET_TC(p) ? "truncated (!) " : "",
truncated ? "truncated (!) " : "",
DNS_PACKET_QR(p) ? "response" : "query",
DNS_PACKET_ID(p),
ifindex, af_to_name(family),
src/resolve/resolved-mdns.c
+2 -1
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@@ -254,8 +254,9 @@ static int mdns_scope_process_query(DnsScope *s, DnsPacket *p) {
if (r < 0)
return log_debug_errno(r, "Failed to extract resource records from incoming packet: %m");
/* TODO: Support Known-Answers only packets gracefully. */
if (dns_question_size(p->question) <= 0)
return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG), "Received mDNS query without question, ignoring.");
return 0;
unicast_reply = mdns_should_reply_using_unicast(p);
if (unicast_reply && !sender_on_local_subnet(s, p)) {