netdev - Re: [PATCH net] ipv4: raw: Fix sending packets from raw sockets via IPsec tunnels

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Date: Fri, 15 Mar 2024 15:31:14 +0100
From: Tobias Brunner <tobias@...ongswan.org>
To: nicolas.dichtel@...nd.com, "David S. Miller" <davem@...emloft.net>,
 David Ahern <dsahern@...nel.org>
Cc: netdev@...r.kernel.org, Steffen Klassert <steffen.klassert@...unet.com>,
 Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH net] ipv4: raw: Fix sending packets from raw sockets via
 IPsec tunnels

>> Since the referenced commit, the xfrm_inner_extract_output() function
>> uses the skb's protocol field to determine the address family.  So not
>> setting it for IPv4 raw sockets meant that such packets couldn't be
>> tunneled via IPsec anymore.
>>
>> IPv6 raw sockets are not affected as they already set the protocol since
>> 9c9c9ad5fae7 ("ipv6: set skb->protocol on tcp, raw and ip6_append_data
>> genereated skbs").
>>
>> Fixes: 5f24f41e8ea6 ("xfrm: Remove inner/outer modes from input path")This is the input part, I presume you were thinking to the output part:
> Fixes: f4796398f21b ("xfrm: Remove inner/outer modes from output path")

Right, will fix.

>> Signed-off-by: Tobias Brunner <tobias@...ongswan.org>
>> ---
>>  net/ipv4/raw.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
>> index 42ac434cfcfa..322e389021c3 100644
>> --- a/net/ipv4/raw.c
>> +++ b/net/ipv4/raw.c
>> @@ -357,6 +357,7 @@ static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4,
>>  		goto error;
>>  	skb_reserve(skb, hlen);
>>  
>> +	skb->protocol = htons(ETH_P_IP);
>>  	skb->priority = READ_ONCE(sk->sk_priority);
>>  	skb->mark = sockc->mark;
>>  	skb->tstamp = sockc->transmit_time;
> For !ipsec packet, dst_output()/ ip_output() is called. This last function set
> skb->protocol to htons(ETH_P_IP).
> What about doing the same in xfrm4_output() to avoid missing another path?

I took this approach because it worked and it aligns the code with the
IPv6 version.  Whether the code path would actually pass through the
function you mention before hitting the problematic one I don't know.

Regards,
Tobias