Re: [PATCH 1/3] tcp: Merge tcp_ns_sock_init[46]() into tcp_sock_init_one()

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Oct 20, 2025 at 08:08:39AM +0200, Stefano Brivio wrote:
> On Fri, 17 Oct 2025 11:34:45 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Surprisingly little logic is shared between the path for creating a
> > listen()ing socket in the guest namespace versus in the host namespace.
> > Improve this, by extending tcp_sock_init_one() to take a pif parameter
> > indicating where it should open the socket.  This allows
> > tcp_ns_sock_init[46]() to be removed entirely.
> > 
> > We generalise tcp_sock_init() in the same way, although we don't use it
> > yet, due to some subtle differences in how we bind for -t versus -T.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  conf.c |  2 +-
> >  tcp.c  | 96 ++++++++++++++++++----------------------------------------
> >  tcp.h  |  5 +--
> >  3 files changed, 33 insertions(+), 70 deletions(-)
> > 
> > diff --git a/conf.c b/conf.c
> > index 66b9e634..26f1bcc0 100644
> > --- a/conf.c
> > +++ b/conf.c
> > @@ -169,7 +169,7 @@ static void conf_ports_range_except(const struct ctx *c, char optname,
> >  		fwd->delta[i] = to - first;
> >  
> >  		if (optname == 't')
> > -			ret = tcp_sock_init(c, addr, ifname, i);
> > +			ret = tcp_sock_init(c, PIF_HOST, addr, ifname, i);
> >  		else if (optname == 'u')
> >  			ret = udp_sock_init(c, 0, addr, ifname, i);
> >  		else
> > diff --git a/tcp.c b/tcp.c
> > index 0f9e9b3f..15c012d7 100644
> > --- a/tcp.c
> > +++ b/tcp.c
> > @@ -2515,29 +2515,38 @@ void tcp_sock_handler(const struct ctx *c, union epoll_ref ref,
> >  /**
> >   * tcp_sock_init_one() - Initialise listening socket for address and port
> >   * @c:		Execution context
> > + * @pif:	Interface to open the socket for (PIF_HOST or PIF_SPLICE)
> >   * @addr:	Pointer to address for binding, NULL for dual stack any
> >   * @ifname:	Name of interface to bind to, NULL if not configured
> >   * @port:	Port, host order
> >   *
> >   * Return: fd for the new listening socket, negative error code on failure
> > + *
> > + * If pif == PIF_SPLICE, must have already entered the namespace.
> >   */
> > -static int tcp_sock_init_one(const struct ctx *c, const union inany_addr *addr,
> > -			     const char *ifname, in_port_t port)
> > +static int tcp_sock_init_one(const struct ctx *c, uint8_t pif,
> > +			     const union inany_addr *addr, const char *ifname,
> > +			     in_port_t port)
> >  {
> > +	const struct fwd_ports *fwd = pif == PIF_HOST ?
> > +		&c->tcp.fwd_in : &c->tcp.fwd_out;
> 
> While I appreciate the resulting brevity, I wonder if it would make
> more sense to have this as an explicit if / else clause, for
> readability. Same for similar occurrences in the next patches (which I
> didn't fully review, yet).
> 
> Another alternative is:
> 
> 	const struct fwd_ports *fwd;
> 
> 	fwd = (pif == PIF_HOST) ? &c->tcp.fwd_in : &c->tcp.fwd_out;
> 
> ...still two lines of code, perhaps just slightly less readable than
> the five obvious ones:
> 
> 	const struct fwd_ports *fwd;
> 
> 	if (pif == PIF_HOST)
> 		fwd = &c->tcp.fwd_in;
> 	else
> 		fwd = &c->tcp.fwd_out;

Good point.  I suspect this will be shuffled again in later patches,
but I might as well go with the less obfuscated version in the
meantime.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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