when the code to handle TCP connect timeouts was moved out of
connect_timeout(), it caused hangs when dig connected via TCP to a
server and the connection succeded but the server never sent a
response. we should add a read timeout mechanism for client TCP
connections as well as a connect timeout mechanism. in the meantime,
however, I've restored the TCP functionality in connect_timeout()
so it can handle the case of read timeouts.
- stop and clean up resources from the TCP connect timer in
isc__nm_tcp_shutdown(), and call the connect callback with
ISC_R_CANCELED
- don't clear TCP queries that are waiting for connect in
clear_query(); they'll be taken care of by tcp_connected() now.
If we clone the csock (children socket) in TCP accept_connection() instead of
passing the ssock (server socket) to the call back and cloning it there we
unbreak the assumption that every socket is handled inside it's own worker
thread and therefore we can get rid of (at least) callback locking.
The uv_udp_connect() function is available from libuv 1.27+, move the code to
connect to udp socket to a (limited) shim function called isc_uv_udp_connect().
Attempting to connect dig to the wrong address via TCP caused a hang on
shutdown due to a dangling socket reference; tcp_connect_cb() was never
reached and so the TCP socket was never detached.
This commit adds a connection timeout mechanism to isc_nm_tcpconnect()
and isc_nm_tcpdnsconnect().
NOTE: Currently this only works correctly with "dig +tries=1". If the
connection is retried, we get a segfault on shutdown in uv_walk(); I
haven't yet worked out why.
when dig is interrupted with SIGINT while a UDP connection is still
pending, it hangs due to recv_done() never being called. adding
an extra handle detach in cancel_all() corrects this, but is probably
not the correct way to fix it.
because dig now uses the netmgr, printing of response messages
happens in a different thread than setup. the IDN output filtering
procedure, which set using dns_name_settotextfilter(), is stored as
thread-local data, and so if it's set during setup, it won't be
accessible when printing. we now set it immediately before printing,
in the same thread, and clear it immedately afterward.
The network manager does not support returning UDP datagrams to
clients from unexpected sources; it is therefore not possible for
dig to accept them. The "+[no]unexpected" option has therefore
been removed from the dig command and its documentation.
- isc_nm_tcpdnsconnect() sets up up an outgoing TCP DNS connection
- isc_nm_udpconnect() sets up a connected UDP socket
- isc_nm_read() now supports UDP; it reads a single datagram and then
stops until the next time it's called.
these functions will later be used to support outgoing queries in dig,
dispatch, etc.
* the legacy test with -T maxudp512 will just fail, e.g. if the packets
larger than 512 octets are dropped along the path, the proper response
is to fail
* digdelv test was just expecting default server EDNS buffer size to be
4096, the test needed only slight adjustment
The DNS Flag Day 2020 aims to remove the IP fragmentation problem from
the UDP DNS communication. In this commit, we implement the required
changes and simplify the logic for picking the EDNS Buffer Size.
1. The defaults for `edns-udp-size`, `max-udp-size` and
`nocookie-udp-size` have been changed to `1232` (the value picked by
DNS Flag Day 2020).
2. The probing heuristics that would try 512->4096->1432->1232 buffer
sizes has been removed and the resolver will always use just the
`edns-udp-size` value.
3. Instead of just disabling the PMTUD mechanism on the UDP sockets, we
now set IP_DONTFRAG (IPV6_DONTFRAG) flag. That means that the UDP
packets won't get ever fragmented. If the ICMP packets are lost the
UDP will just timeout and eventually be retried over TCP.
The SO_REUSEADDR, SO_REUSEPORT and SO_REUSEPORT_LB has different meaning
on different platform. In this commit, we split the function to set the
reuse of address/port and setting the load-balancing into separate
functions.
The libuv library already have multiplatform support for setting
SO_REUSEADDR and SO_REUSEPORT that allows binding to the same address
and port, but unfortunately, when used after the load-balancing socket
options have been already set, it overrides the previous setting, so we
need our own helper function to enable the SO_REUSEADDR/SO_REUSEPORT
first and then enable the load-balancing socket option.
On POSIX based systems both uv_os_sock_t and uv_os_fd_t are both typedef
to int. That's not true on Windows, where uv_os_sock_t is SOCKET and
uv_os_fd_t is HANDLE and they differ in level of indirection.
The isc__nm_socket_freebind() has been refactored to match other
isc__nm_socket_...() helper functions and take uv_os_fd_t and
sa_family_t as function arguments.
While working on 'rndc dnssec -rollover' I noticed the following
(small) issues:
- The key files where updated with hints set to "-when" and that
should always be "now.
- The kasp system test did not properly update the test number when
calling 'rndc dnssec -checkds' (and ensuring that works).
- There was a missing ']' in the rndc.c help output.
Evan Hunt
Ondřej SurýandEvan Hunt
Mark Andrews
Matthijs Mekking
Havard EidnesandMatthijs Mekking
Ondřej Surý