Hi David, Yes, you are right, I overlooked this. Unfortunately the current receive process in the DCCP layer does from my view not properly support the skb->ip_summed flag verification, because the checksum validation takes place at different places. This would require some dirty hacks...
I see two options. 1. Adding the ip_summed flag verification or 2. Learn from the UDP stack Since UDP/UDP-Lite are very similar to DCCP, at least from a checksum verification point, I ask myself if it would make sense to re-work DCCP's receive process according to the one of UDP/UDP-Lite? The relevant process in the udp stack (for IPv4) I identified therefore, can be found in /net/ipv4/udp.c, within the function __udp4_lib_rcv. There it is done, compared to DCCP, the other way round it starts with an udp4_csum_init and most likely a later udp_lib_checksum_complete. Both consider skb->ip_summed. If we would implement similar functions into the DCCP stack and adapt the DCCP rcv checksum validation process to the one in UDP could make probably more sense?! Personally I prefer the second option, what do you think? BR Markus > -----Original Message----- > From: David Miller <da...@davemloft.net> > Sent: Sonntag, 5. Mai 2019 18:53 > To: Amend, Markus <markus.am...@telekom.de> > Cc: linux-kernel@vger.kernel.org; net...@vger.kernel.org; > d...@vger.kernel.org > Subject: Re: [PATCH v3] net: dccp: Checksum verification enhancement > > From: <markus.am...@telekom.de> > Date: Tue, 30 Apr 2019 16:11:07 +0000 > > > The current patch modifies the checksum verification of a received > > DCCP packet, by adding the function __skb_checksum_validate into the > > dccp_vX_rcv routine. The purpose of the modification is to allow the > > verification of the skb->ip_summed flags during the checksum > > validation process (for checksum offload purposes). As > > __skb_checksum_validate covers the functionalities of skb_checksum and > > dccp_vX_csum_finish they are needless and therefore removed. > > > > Signed-off-by: Nathalie Romo Moreno <natha.ro.mor...@gmail.com> > > Signed-off-by: Markus Amend <markus.am...@telekom.de> > > I don't see how this can be correct as you're not taking the csum coverage > value into consideration at all.
