MEDIUM: dns: adds code to support pipelined DNS requests over TCP.
This patch introduce the "dns_stream_nameserver" to use DNS over
TCP on strict nameservers. For the upper layer it is analog to
the api used with udp nameservers except that the user que switch
the name server in "stream" mode at the init using "dns_stream_init".
The fallback from UDP to TCP is not handled and this is not the
purpose of this feature. This is done to choose the transport layer
during the initialization.
Currently there is a hardcoded limit of 4 pipelined transactions
per TCP connections. A batch of idle connections is expired every 5s.
This code is designed to support a maximum DNS message size on TCP: 64k.
Note: this code won't perform retry on unanswered queries this
should be handled by the upper layer
3 files changed