| Message ID | FRAPR01MB11707401056D4D6C95D8C615FA3A0@FRAPR01MB1170.DEUPRD01.PROD.OUTLOOK.DE |
|---|---|
| State | Rejected |
| Delegated to: | David Miller |
| Headers | show |
| Series | [v3] net: dccp: Checksum verification enhancement | expand |
From: <Markus.Amend@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.moreno@gmail.com> > Signed-off-by: Markus Amend <markus.amend@telekom.de> I don't see how this can be correct as you're not taking the csum coverage value into consideration at all.
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 <davem@davemloft.net> > Sent: Sonntag, 5. Mai 2019 18:53 > To: Amend, Markus <Markus.Amend@telekom.de> > Cc: linux-kernel@vger.kernel.org; netdev@vger.kernel.org; > dccp@vger.kernel.org > Subject: Re: [PATCH v3] net: dccp: Checksum verification enhancement > > From: <Markus.Amend@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.moreno@gmail.com> > > Signed-off-by: Markus Amend <markus.amend@telekom.de> > > I don't see how this can be correct as you're not taking the csum coverage > value into consideration at all.
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c index 26a21d97b6b0..ca4eb93e4663 100644 --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -762,9 +762,6 @@ int dccp_invalid_packet(struct sk_buff *skb) return 1; } - /* If header checksum is incorrect, drop packet and return. - * (This step is completed in the AF-dependent functions.) */ - skb->csum = skb_checksum(skb, 0, cscov, 0); return 0; } @@ -786,7 +783,8 @@ static int dccp_v4_rcv(struct sk_buff *skb) iph = ip_hdr(skb); /* Step 1: If header checksum is incorrect, drop packet and return */ - if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) { + if (__skb_checksum_validate(skb, IPPROTO_DCCP, + true, false, 0, inet_compute_pseudo)) { DCCP_WARN("dropped packet with invalid checksum\n"); goto discard_it; } diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c index d5740bad5b18..22df24fecfe7 100644 --- a/net/dccp/ipv6.c +++ b/net/dccp/ipv6.c @@ -694,9 +694,9 @@ static int dccp_v6_rcv(struct sk_buff *skb) if (dccp_invalid_packet(skb)) goto discard_it; - /* Step 1: If header checksum is incorrect, drop packet and return. */ - if (dccp_v6_csum_finish(skb, &ipv6_hdr(skb)->saddr, - &ipv6_hdr(skb)->daddr)) { + /* Step 1: If header checksum is incorrect, drop packet and return */ + if (__skb_checksum_validate(skb, IPPROTO_DCCP, + true, false, 0, ip6_compute_pseudo)) { DCCP_WARN("dropped packet with invalid checksum\n"); goto discard_it; }