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Clarify KEEPALIVE EDNS0 option operation

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This commit is contained in:
Tom Carpay 2021-11-15 14:00:31 +00:00
parent e899b4cefe
commit ff030fa332
1 changed files with 12 additions and 0 deletions
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12
util/data/msgparse.c
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@ -961,6 +961,10 @@ parse_edns_options_from_query(uint8_t* rdata_ptr, size_t rdata_len,
* received one message with a TCP Keepalive EDNS option, and that
* option must have 0 length data. Subsequent messages sent on that
* connection will have a TCP Keepalive option.
*
* In the if-statement below, the option is added unsolicited. This
* means that the client has sent an KEEPALIVE option earlier. We know
* here this is true, because c->tcp_keepalive is set.
*/
if (cfg && cfg->do_tcp_keepalive && c && c->type != comm_udp && c->tcp_keepalive) {
if(!edns_opt_list_append_keepalive(&edns->opt_list_out,
@ -999,6 +1003,14 @@ parse_edns_options_from_query(uint8_t* rdata_ptr, size_t rdata_len,
* Keepalive EDNS option, and that option must have 0
* length data. Subsequent messages sent on that
* connection will have a TCP Keepalive option.
*
* This should be the first time the client sends this
* option, so c->tcp_keepalive is not set.
* Besides adding the reply KEEPALIVE option,
* c->tcp_keepalive will be set so that the
* option will be added unsolicited in subsequent
* responses (see the comment above the if-statement
* at the start of this function).
*/
if (!cfg || !cfg->do_tcp_keepalive || !c ||
c->type == comm_udp || c->tcp_keepalive)