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

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Date:   Thu, 12 May 2022 16:02:20 +0300
From:   Aya Levin <ayal@...dia.com>
To:     David Ahern <dsahern@...nel.org>, Tariq Toukan <tariqt@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, Gal Pressman <gal@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>
Subject: Re: [PATCH net] net: ping6: Fix ping -6 with interface name



On 5/10/2022 11:27 PM, David Ahern wrote:
> On 5/10/22 11:27 AM, Tariq Toukan wrote:
>> From: Aya Levin <ayal@...dia.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.
>>
>> Fixes: 13651224c00b ("net: ping6: support setting basic SOL_IPV6 options via cmsg")
>> Signed-off-by: Aya Levin <ayal@...dia.com>
>> Reviewed-by: Gal Pressman <gal@...dia.com>
>> Reviewed-by: Saeed Mahameed <saeedm@...dia.com>
>> Signed-off-by: Tariq Toukan <tariqt@...dia.com>
>> ---
>>   net/ipv6/ping.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
>> index ff033d16549e..83f014559c0d 100644
>> --- a/net/ipv6/ping.c
>> +++ b/net/ipv6/ping.c
>> @@ -106,6 +106,8 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>>   
>>   		opt.tot_len = sizeof(opt);
>>   		ipc6.opt = &opt;
>> +		memset(&fl6, 0, sizeof(fl6));
>> +		fl6.flowi6_oif = oif;
>>   
>>   		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6);
>>   		if (err < 0)
> 
> I agree that fl6 is used unitialized here, but right after this is:
> 
>          memset(&fl6, 0, sizeof(fl6));
> 
>          fl6.flowi6_proto = IPPROTO_ICMPV6;
>          fl6.saddr = np->saddr;
>          fl6.daddr = *daddr;
>          fl6.flowi6_oif = oif;
> 
> so adding a memset before the call to ip6_datagram_send_ctl duplicates
> the existing one. Best to move the memset before the 'if
> (msg->msg_controllen) {'
Hi,

Thanks for your comment. As far as I understand the flow, any changes 
done to fl6 inside ip6_datagram_send_ctl is to be disregarded. That's 
how I understand the comment:
/* Changes to txoptions and flow info are not implemented, yet.
  * Drop the options, fl6 is wiped below.
  */

Thanks,
Aya