Re: [PATCH v3 12/15] icmp: Populate and use host side flow information

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 21 Dec 2023 18:02:34 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> Complete filling out the common flow information for "ping" flows by
> storing the host side information for the ping socket.  We can only
> retrieve this from the socket after we send the echo-request, because
> that's when the kernel will assign an ID.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  icmp.c | 36 +++++++++++++++++++++++++++++++++---
>  1 file changed, 33 insertions(+), 3 deletions(-)
> 
> diff --git a/icmp.c b/icmp.c
> index 53ad087..917c810 100644
> --- a/icmp.c
> +++ b/icmp.c
> @@ -310,11 +310,41 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
>  	if (sendto(pingf->sock, pkt, plen, MSG_NOSIGNAL, &sa.sa, sl) < 0) {
>  		debug("%s: failed to relay request to socket: %s",
>  		      pname, strerror(errno));
> -	} else {
> -		debug("%s: echo request to socket, ID: %"PRIu16", seq: %"PRIu16,
> -		      pname, id, seq);
> +		if (flow)
> +			goto cancel;
> +	}
> +
> +	debug("%s: echo request to socket, ID: %"PRIu16", seq: %"PRIu16,
> +	      pname, id, seq);
> +
> +	if (!flow)
> +		/* Nothing more to do for an existing flow */
> +		return 1;
> +
> +	/* We need to wait until after the sendto() to fill in the SOCKSIDE
> +	 * information, so that we can find out the host side id the kernel
> +	 * assigned.  If there's no bind address specified, this will still have
> +	 * 0.0.0.0 or :: as the host side forwarding address.  There's not
> +	 * really anything we can do to fill that in, which means we can never
> +	 * insert the SOCKSIDE of a ping flow into the hash table.
> +	 */

Well, if it was just because of that we could argue at some point that,
with wildcards or suchlike, we could insert that in the hash table as
well.

But that wouldn't make sense anyway, right? That is, unless I'm missing
something, we would have no use for a hash table lookup of the SOCKSIDE
of a ping flow anyway.

Patches 13/15 to 15/15 all look good to me.

-- 
Stefano