Re: [RFC nf-next v2 1/2] netfilter: connmark: introduce savedscp

[Kevin 'ldir' Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>]

Hi Pablo,

Thanks for review.  Some answers inline

> On 30 Apr 2019, at 13:29, Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> 
> On Tue, Apr 09, 2019 at 02:23:46PM +0000, Kevin 'ldir' Darbyshire-Bryant wrote:
>> diff --git a/include/uapi/linux/netfilter/xt_connmark.h b/include/uapi/linux/netfilter/xt_connmark.h
>> index 1aa5c955ee1e..24272cac2d37 100644
>> --- a/include/uapi/linux/netfilter/xt_connmark.h
>> +++ b/include/uapi/linux/netfilter/xt_connmark.h
>> @@ -16,7 +16,8 @@
>> enum {
>> 	XT_CONNMARK_SET = 0,
>> 	XT_CONNMARK_SAVE,
>> -	XT_CONNMARK_RESTORE
>> +	XT_CONNMARK_RESTORE,
>> +	XT_CONNMARK_SAVEDSCP
> 
> I'd prefer you implement this in nftables, more comments below.

I will look into this. nftables is new to me.

> 
>> };
>> 
>> enum {
>> diff --git a/net/netfilter/xt_connmark.c b/net/netfilter/xt_connmark.c
>> index 29c38aa7f726..6c63cf476342 100644
>> --- a/net/netfilter/xt_connmark.c
>> +++ b/net/netfilter/xt_connmark.c
>> @@ -42,6 +42,7 @@ connmark_tg_shift(struct sk_buff *skb, const struct xt_connmark_tginfo2 *info)
>> 	u_int32_t new_targetmark;
>> 	struct nf_conn *ct;
>> 	u_int32_t newmark;
>> +	u8 dscp;
>> 
>> 	ct = nf_ct_get(skb, &ctinfo);
>> 	if (ct == NULL)
>> @@ -74,6 +75,34 @@ connmark_tg_shift(struct sk_buff *skb, const struct xt_connmark_tginfo2 *info)
>> 			nf_conntrack_event_cache(IPCT_MARK, ct);
>> 		}
>> 		break;
>> +	case XT_CONNMARK_SAVEDSCP:
> 
> Could you add a new revision and a new flag field for this? so it just
> adds the dscp to the mark as you need.

Not sure I understand this.  Do you mean make it part of XT_CONNMARK_SAVE
and have something like ‘info->dscpmask’?  If (!info->dscpmask) do dscp
stuff else do the original routine?

> 
>> +		if (!info->ctmark)
>> +			goto out;
>> +
>> +		if (skb->protocol == htons(ETH_P_IP)) {
>> +			if (skb->len < sizeof(struct iphdr))
>> +				goto out;
>> +
>> +			dscp = ipv4_get_dsfield(ip_hdr(skb)) >> 2;
>> +
>> +		} else if (skb->protocol == htons(ETH_P_IPV6)) {
>> +			if (skb->len < sizeof(struct ipv6hdr))
>> +				goto out;
> 
> This is already guaranteed to have a valid IP header in place, no need
> for this check.

Ok, thanks - removing code is easy (and faster) :-)

Once again thanks for your review & time.

> 
>> +
>> +			dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> 2;
>> +
>> +		} else { /* protocol doesn't have diffserv - get out! */
>> +			goto out;
>> +		}
>> +
>> +		newmark = (ct->mark & ~info->ctmark) ^
>> +			  (info->ctmask | (dscp << info->shift_bits));
>> +
>> +		if (ct->mark != newmark) {
>> +			ct->mark = newmark;
>> +			nf_conntrack_event_cache(IPCT_MARK, ct);
>> +		}
>> +		break;
>> 	case XT_CONNMARK_RESTORE:
>> 		new_targetmark = (ct->mark & info->ctmask);
>> 		if (info->shift_dir == D_SHIFT_RIGHT)
>> @@ -86,6 +115,7 @@ connmark_tg_shift(struct sk_buff *skb, const struct xt_connmark_tginfo2 *info)
>> 		skb->mark = newmark;
>> 		break;
>> 	}
>> +out:
>> 	return XT_CONTINUE;
>> }
>> 
>> -- 
>> 2.20.1 (Apple Git-117)
>> 


Cheers,

Kevin D-B

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