On 21.11.2024 23:23, Antonio Quartulli wrote:
On 21/11/2024 00:22, Sergey Ryazanov wrote:
On 13.11.2024 12:03, Sabrina Dubroca wrote:
2024-11-13, 03:37:13 +0200, Sergey Ryazanov wrote:
On 12.11.2024 19:31, Sabrina Dubroca wrote:
2024-11-10, 15:38:27 +0200, Sergey Ryazanov wrote:
On 29.10.2024 12:47, Antonio Quartulli wrote:
An ovpn_peer object holds the whole status of a remote peer
(regardless whether it is a server or a client).
This includes status for crypto, tx/rx buffers, napi, etc.
Only support for one peer is introduced (P2P mode).
Multi peer support is introduced with a later patch.
Reviewing the peer creation/destroying code I came to a generic
question.
Did you consider keeping a single P2P peer in the peers table as
well?
Looks like such approach can greatly simply the code by dropping
all these
'switch (ovpn->mode)' checks and implementing a unified peer
management. The
'peer' field in the main private data structure can be kept to
accelerate
lookups, still using peers table for management tasks like
removing all the
peers on the interface teardown.
It would save a few 'switch(mode)', but force every client to allocate
the hashtable for no reason at all. That tradeoff doesn't look very
beneficial to me, the P2P-specific code is really simple. And if you
keep ovpn->peer to make lookups faster, you're not removing that many
'switch(mode)'.
Looking at the done review, I can retrospectively conclude that I
personally
do not like short 'switch' statements and special handlers :)
Seriously, this module has a highest density of switches per KLOC
from what
I have seen before and a major part of it dedicated to handle the
special
case of P2P connection.
I think it's fine. Either way there will be two implementations of
whatever mode-dependent operation needs to be done. switch doesn't
make it more complex than an ops structure.
If you're reading the current version and find ovpn_peer_add, you see
directly that it'll do either ovpn_peer_add_mp or
ovpn_peer_add_p2p. With an ops structure, you'd have a call to
ovpn->ops->peer_add, and you'd have to look up all possible ops
structures to know that it can be either ovpn_peer_add_mp or
ovpn_peer_add_p2p. If there's an undefined number of implementations
living in different modules (like net_device_ops, or L4 protocols),
you don't have a choice.
xfrm went the opposite way to what you're proposing a few years ago
(see commit 0c620e97b349 ("xfrm: remove output indirection from
xfrm_mode") and others), and it made the code simpler.
I checked this. Florian did a nice rework. And the way of
implementation looks reasonable since there are more than two
encapsulation modes and handling is more complex than just selecting a
function to call.
What I don't like about switches, that it requires extra lines of code
and pushes an author to introduce a default case with error handling.
It was mentioned that the module unlikely going to support more than
two modes. In this context shall we consider ternary operator usage.
E.g.:
the default case can actually be dropped. That way we can have the
compiler warn when one of the enum values is not handled in the switch
(should there be a new one at some point).
However, the default is just a sanity check against future code changes
which may introduce a bug.
next_run = ovpn->mode == OVPN_MODE_P2P ?
ovpn_peer_keepalive_work_p2p(...) :
ovpn_peer_keepalive_work_mp(...);
I find this ugly to read :-)
Yeah. Doesn't look pretty as well.
Just to conclude the discussion. Considering what we discussed here and
the Sabrina's point regarding the trampoline penalty for indirect
invocation, we do not have a better solution for now other than using
switches everywhere.
--
Sergey
