resolved: for a transaction, keep track where the answer data came from

Let's track where the data came from: from the network, the cache or the
local zone. This is not only useful for debugging purposes, but is also
useful when the zone probing wants to ensure it's not reusing
transactions that were answered from the cache or the zone itself.

1 files changed, 16 insertions, 2 deletions

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index ef5097db39..519358ffb1 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -103,6 +103,7 @@ int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key)
                 return -ENOMEM;
 
         t->dns_udp_fd = -1;
+        t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID;
         t->key = dns_resource_key_ref(key);
 
         /* Find a fresh, unused transaction id */
@@ -197,11 +198,12 @@ void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) {
          * should hence not attempt to access the query or transaction
          * after calling this function. */
 
-        log_debug("Transaction on scope %s on %s/%s now complete with <%s>",
+        log_debug("Transaction on scope %s on %s/%s now complete with <%s> from %s",
                   dns_protocol_to_string(t->scope->protocol),
                   t->scope->link ? t->scope->link->name : "*",
                   t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family),
-                  dns_transaction_state_to_string(state));
+                  dns_transaction_state_to_string(state),
+                  t->answer_source < 0 ? "none" : dns_transaction_source_to_string(t->answer_source));
 
         t->state = state;
 
@@ -392,6 +394,8 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
                 t->received = dns_packet_ref(p);
         }
 
+        t->answer_source = DNS_TRANSACTION_NETWORK;
+
         if (p->ipproto == IPPROTO_TCP) {
                 if (DNS_PACKET_TC(p)) {
                         /* Truncated via TCP? Somebody must be fucking with us */
@@ -637,6 +641,7 @@ int dns_transaction_go(DnsTransaction *t) {
         t->received = dns_packet_unref(t->received);
         t->answer = dns_answer_unref(t->answer);
         t->answer_rcode = 0;
+        t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID;
 
         /* Check the zone, but obly if this transaction is not used
          * for probing or verifying a zone item. */
@@ -647,6 +652,7 @@ int dns_transaction_go(DnsTransaction *t) {
                         return r;
                 if (r > 0) {
                         t->answer_rcode = DNS_RCODE_SUCCESS;
+                        t->answer_source = DNS_TRANSACTION_ZONE;
                         dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
                         return 0;
                 }
@@ -668,6 +674,7 @@ int dns_transaction_go(DnsTransaction *t) {
                 if (r < 0)
                         return r;
                 if (r > 0) {
+                        t->answer_source = DNS_TRANSACTION_CACHE;
                         if (t->answer_rcode == DNS_RCODE_SUCCESS)
                                 dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
                         else
@@ -771,3 +778,10 @@ static const char* const dns_transaction_state_table[_DNS_TRANSACTION_STATE_MAX]
         [DNS_TRANSACTION_ABORTED] = "aborted",
 };
 DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state, DnsTransactionState);
+
+static const char* const dns_transaction_source_table[_DNS_TRANSACTION_SOURCE_MAX] = {
+        [DNS_TRANSACTION_NETWORK] = "network",
+        [DNS_TRANSACTION_CACHE] = "cache",
+        [DNS_TRANSACTION_ZONE] = "zone",
+};
+DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source, DnsTransactionSource);