We strips out NLMSG_DONE piece from a multi-part message adding into the
receive queue only the messages containing actual data.
If we send a request to the kernel for getting the forwarding database table (just an example),
the response will be a multi-part message like below:
1. FDB entry 1;
2. FDB entry 2;
3. NLMSG_DONE;
We strip out "3. NLMSG_DONE;" part and places into the receive queue a pointer to
"1. FDB entry 1; 2. FDB entry 2".
But if the FDB table is empty, the respose from the kernel will look like below:
1. NLMSG_DONE;
We strip out "1. NLMSG_DONE;" part and since there is no actual data got, it continues
waiting until reaching timeout.
Therefore, a call to "sd_rtnl_call" to send and wait for a response from kernel will exit
with timeout which is interpreted as error in communication.
This patch puts the NLMSG_DONE message on the receive queue if it ends an empty multi-part
message. This situation is detected in sd_rtnl_call() and in the callback code and NULL is
returned to the caller instead.
[tomegun:
- added/reworded commit message
- extend the same support to sd_rtnl_call_async()
- drop debug logging from library, we only do this if something is really wrong, but an
empty multi-part message is perfectly normal
- modernize the code we touch whilst we are at it]
Introduce BindCarrier= to indicate the set of links that determine if
the current link should be brought UP or DOWN.
[tomegun: add a bit to commit message]
We got the following error when running systemd on a device with many ports:
"rtnl: kernel receive buffer overrun
Event source 'rtnl-receive-message' returned error, disabling: No buffer space
available"
I think the kernel socket receive buffer queue should be increased. The default
value is taken from:
"/proc/sys/net/core/rmem_default", but we can overwrite it using SO_RCVBUF
socket option.
This is already done in networkd for other sockets.
For example, the bus socket (sd-bus/bus-socket.c) has a receive queue of 8MB.
In our case, the default is 208KB.
Increasing the buffer receive queue for manager socket to 512KB should be enough
to get rid of the above error.
[tomegun: bump the limit even higher to 8M]
Alin Rauta