Re: [PATCH net V2] net: ping6: Fix ping -6 with interface name

[David Ahern <dsahern@kernel.org>]

On 5/29/22 5:50 AM, Tariq Toukan wrote:
> From: Aya Levin <ayal@nvidia.com>
> 
> When passing interface parameter to ping -6:
> $ ping -6 ::11:141:84:9 -I eth2
> Results in:
> PING ::11:141:84:10(::11:141:84:10) from ::11:141:84:9 eth2: 56 data bytes
> ping: sendmsg: Invalid argument
> ping: sendmsg: Invalid argument
> 
> Initialize the fl6's outgoing interface (OIF) before triggering
> ip6_datagram_send_ctl. Don't wipe fl6 after ip6_datagram_send_ctl() as
> changes in fl6 that may happen in the function are overwritten explicitly.
> Update comment accordingly.
> 
> Fixes: 13651224c00b ("net: ping6: support setting basic SOL_IPV6 options via cmsg")
> Signed-off-by: Aya Levin <ayal@nvidia.com>
> Reviewed-by: Gal Pressman <gal@nvidia.com>
> Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
> Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
> ---
>  net/ipv6/ping.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> V2:
> Per David Ahern's comment, moved memset before if (msg->msg_controllen),
> and updated the code comment accordingly.
> 
> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
> index ff033d16549e..2a5f3337d488 100644
> --- a/net/ipv6/ping.c
> +++ b/net/ipv6/ping.c
> @@ -101,24 +101,25 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>  	ipc6.sockc.tsflags = sk->sk_tsflags;
>  	ipc6.sockc.mark = sk->sk_mark;
>  
> +	memset(&fl6, 0, sizeof(fl6));
> +
>  	if (msg->msg_controllen) {
>  		struct ipv6_txoptions opt = {};
>  
>  		opt.tot_len = sizeof(opt);
>  		ipc6.opt = &opt;
> +		fl6.flowi6_oif = oif;

This should be moved up to after the memset since it is currently done
after "fl6.daddr = *daddr;" below (remove that one). That's how it is
done in rawv6_sendmsg and udpv6_sendmsg.



>  
>  		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6);
>  		if (err < 0)
>  			return err;
>  
>  		/* Changes to txoptions and flow info are not implemented, yet.
> -		 * Drop the options, fl6 is wiped below.
> +		 * Drop the options.
>  		 */
>  		ipc6.opt = NULL;
>  	}
>  
> -	memset(&fl6, 0, sizeof(fl6));
> -
>  	fl6.flowi6_proto = IPPROTO_ICMPV6;
>  	fl6.saddr = np->saddr;
>  	fl6.daddr = *daddr;