Re: [PATCH v2 04/16] udp: Don't connect "forward" sockets for spliced flows

[Stefano Brivio <sbrivio@redhat.com>]

On Fri, 25 Nov 2022 18:07:32 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Fri, Nov 25, 2022 at 02:47:59AM +0100, Stefano Brivio wrote:
> > Nit:
> > 
> > On Thu, 24 Nov 2022 12:16:47 +1100
> > David Gibson <david@gibson.dropbear.id.au> wrote:
> >   
> > > Currently we connect() the socket we use to forward spliced UDP flows.
> > > However, we now only ever use sendto() rather than send() on this socket
> > > so there's not actually any need to connect it.  Don't do so.
> > > 
> > > Rename a number of things that referred to "connect" or "conn" since that
> > > would now be misleading.
> > > 
> > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > > ---
> > >  udp.c | 85 ++++++++++++++++++++++++-----------------------------------
> > >  1 file changed, 35 insertions(+), 50 deletions(-)
> > > 
> > > diff --git a/udp.c b/udp.c
> > > index 1e78da5..ed095ec 100644
> > > --- a/udp.c
> > > +++ b/udp.c
> > > @@ -45,23 +45,20 @@
> > >   *
> > >   * - from init to namespace:
> > >   *
> > > - *   - forward direction: 127.0.0.1:5000 -> 127.0.0.1:80 in init from bound
> > > - *     socket s, with epoll reference: index = 80, splice = UDP_TO_NS
> > > + *   - forward direction: 127.0.0.1:5000 -> 127.0.0.1:80 in init from socket s,
> > > + *     with epoll reference: index = 80, splice = UDP_TO_NS
> > >   *     - if udp_splice_to_ns[V4][5000].target_sock:
> > >   *       - send packet to udp_splice_to_ns[V4][5000].target_sock, with
> > >   *         destination port 80
> > >   *     - otherwise:
> > >   *       - create new socket udp_splice_to_ns[V4][5000].target_sock
> > >   *       - bind in namespace to 127.0.0.1:5000
> > > - *       - connect in namespace to 127.0.0.1:80 (note: this destination port
> > > - *         might be remapped to another port instead)
> > >   *       - add to epoll with reference: index = 5000, splice: UDP_BACK_TO_INIT
> > >   *       - set udp_splice_to_ns[V4][5000].orig_sock to s
> > >   *     - update udp_splice_to_ns[V4][5000].ts with current time
> > >   *
> > > - *   - reverse direction: 127.0.0.1:80 -> 127.0.0.1:5000 in namespace from
> > > - *     connected socket s, having epoll reference: index = 5000,
> > > - *     splice = UDP_BACK_TO_INIT
> > > + *   - reverse direction: 127.0.0.1:80 -> 127.0.0.1:5000 in namespace socket s,
> > > + *     having epoll reference: index = 5000, splice = UDP_BACK_TO_INIT
> > >   *     - if udp_splice_to_ns[V4][5000].orig_sock:
> > >   *       - send to udp_splice_to_ns[V4][5000].orig_sock, with destination port
> > >   *         5000
> > > @@ -69,7 +66,7 @@
> > >   *
> > >   * - from namespace to init:
> > >   *
> > > - *   - forward direction: 127.0.0.1:2000 -> 127.0.0.1:22 in namespace from bound
> > > + *   - forward direction: 127.0.0.1:2000 -> 127.0.0.1:22 in namespace from
> > >   *     socket s, with epoll reference: index = 22, splice = UDP_TO_INIT
> > >   *     - if udp4_splice_to_init[V4][2000].target_sock:
> > >   *       - send packet to udp_splice_to_init[V4][2000].target_sock, with
> > > @@ -77,14 +74,12 @@
> > >   *     - otherwise:
> > >   *       - create new socket udp_splice_to_init[V4][2000].target_sock
> > >   *       - bind in init to 127.0.0.1:2000
> > > - *       - connect in init to 127.0.0.1:22 (note: this destination port
> > > - *         might be remapped to another port instead)
> > >   *       - add to epoll with reference: index = 2000, splice = UDP_BACK_TO_NS
> > >   *       - set udp_splice_to_init[V4][2000].orig_sock to s
> > >   *     - update udp_splice_to_init[V4][2000].ts with current time
> > >   *
> > > - *   - reverse direction: 127.0.0.1:22 -> 127.0.0.1:2000 in init from connected
> > > - *     socket s, having epoll reference: index = 2000, splice = UDP_BACK_TO_NS
> > > + *   - reverse direction: 127.0.0.1:22 -> 127.0.0.1:2000 in init from socket s,
> > > + *     having epoll reference: index = 2000, splice = UDP_BACK_TO_NS
> > >   *   - if udp_splice_to_init[V4][2000].orig_sock:
> > >   *     - send to udp_splice_to_init[V4][2000].orig_sock, with destination port
> > >   *       2000
> > > @@ -144,8 +139,7 @@ struct udp_tap_port {
> > >   * @orig_sock:		Originating socket, bound to dest port in source ns of
> > >   *			originating datagram
> > >   * @target_sock:	Target socket, bound to source port of originating
> > > - *			datagram in dest ns, connected to dest port of
> > > - *			originating datagram in dest ns
> > > + *			datagram in dest ns
> > >   * @ts:			Activity timestamp
> > >   */
> > >  struct udp_splice_flow {
> > > @@ -163,8 +157,8 @@ static struct udp_splice_flow udp_splice_to_init[IP_VERSIONS][NUM_PORTS];
> > >  
> > >  enum udp_act_type {
> > >  	UDP_ACT_TAP,
> > > -	UDP_ACT_NS_CONN,
> > > -	UDP_ACT_INIT_CONN,
> > > +	UDP_ACT_SPLICE_NS,
> > > +	UDP_ACT_SPLICE_INIT,
> > >  	UDP_ACT_TYPE_MAX,
> > >  };
> > >  
> > > @@ -398,20 +392,19 @@ static void udp_sock6_iov_init(void)
> > >  }
> > >  
> > >  /**
> > > - * udp_splice_connect() - Create and connect socket for "spliced" binding
> > > + * udp_splice_new() - Create and prepare socket for "spliced" binding
> > >   * @c:		Execution context
> > > - * @v6:		Set for IPv6 connections
> > > + * @v6:		Set for IPv6 sockets
> > >   * @bound_sock:	Originating bound socket
> > >   * @src:	Source port of original connection, host order
> > > - * @dst:	Destination port of original connection, host order
> > >   * @splice:	UDP_BACK_TO_INIT from init, UDP_BACK_TO_NS from namespace
> > >   *
> > > - * Return: connected socket, negative error code on failure
> > > + * Return: Prepared socket, negative error code on failure  
> > 
> > prepared  
> 
> Fixed.  Is there a particular rationale for capitalizing on the
> parameters, but not the return description?

Sorry, I started reviewing your v4 and noticed I forgot to answer this.
It's actually inconsistent with the Kernel-doc style which pretty much
inspires this:
  https://docs.kernel.org/doc-guide/kernel-doc.html

so I started like that because in kernel's net/ directory the
non-capitalised version is more common:

  $ grep -rnI "Return: [A-Z][ a-z]" | wc -l
  66
  $ grep -rnI "Return: [a-z]" | wc -l
  298

and I'm simply used to that -- but it's also true I added 19 of those.
My very personal interpretation of the rationale is that in this case we
form a sentence, and at the same time sentences certainly don't start
with '@'.

Actually, if we capitalise them, we could at least refer to those as
coding style guidelines. :) I'd rather "fix" this all at once when we
get to https://bugs.passt.top/show_bug.cgi?id=35.

-- 
Stefano