Re: [PATCH v3 bpf-next 4/5] net: netfilter: add kfunc helper to add a new ct entry

[Lorenzo Bianconi <lorenzo.bianconi@redhat.com>]

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> Lorenzo Bianconi <lorenzo@kernel.org> writes:
> 
> > Introduce bpf_xdp_ct_add and bpf_skb_ct_add kfunc helpers in order to
> > add a new entry to ct map from an ebpf program.
> > Introduce bpf_nf_ct_tuple_parse utility routine.
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> > ---
> >  net/netfilter/nf_conntrack_bpf.c | 212 +++++++++++++++++++++++++++----
> >  1 file changed, 189 insertions(+), 23 deletions(-)
> >
> > diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c
> > index a9271418db88..3d31b602fdf1 100644
> > --- a/net/netfilter/nf_conntrack_bpf.c
> > +++ b/net/netfilter/nf_conntrack_bpf.c
> > @@ -55,41 +55,114 @@ enum {
> >  	NF_BPF_CT_OPTS_SZ = 12,
> >  };
> >  
> > -static struct nf_conn *__bpf_nf_ct_lookup(struct net *net,
> > -					  struct bpf_sock_tuple *bpf_tuple,
> > -					  u32 tuple_len, u8 protonum,
> > -					  s32 netns_id, u8 *dir)
> > +static int bpf_nf_ct_tuple_parse(struct bpf_sock_tuple *bpf_tuple,
> > +				 u32 tuple_len, u8 protonum, u8 dir,
> > +				 struct nf_conntrack_tuple *tuple)
> >  {
> > -	struct nf_conntrack_tuple_hash *hash;
> > -	struct nf_conntrack_tuple tuple;
> > -	struct nf_conn *ct;
> > +	union nf_inet_addr *src = dir ? &tuple->dst.u3 : &tuple->src.u3;
> > +	union nf_inet_addr *dst = dir ? &tuple->src.u3 : &tuple->dst.u3;
> > +	union nf_conntrack_man_proto *sport = dir ? (void *)&tuple->dst.u
> > +						  : &tuple->src.u;
> > +	union nf_conntrack_man_proto *dport = dir ? &tuple->src.u
> > +						  : (void *)&tuple->dst.u;
> >  
> >  	if (unlikely(protonum != IPPROTO_TCP && protonum != IPPROTO_UDP))
> > -		return ERR_PTR(-EPROTO);
> > -	if (unlikely(netns_id < BPF_F_CURRENT_NETNS))
> > -		return ERR_PTR(-EINVAL);
> > +		return -EPROTO;
> > +
> > +	memset(tuple, 0, sizeof(*tuple));
> >  
> > -	memset(&tuple, 0, sizeof(tuple));
> >  	switch (tuple_len) {
> >  	case sizeof(bpf_tuple->ipv4):
> > -		tuple.src.l3num = AF_INET;
> > -		tuple.src.u3.ip = bpf_tuple->ipv4.saddr;
> > -		tuple.src.u.tcp.port = bpf_tuple->ipv4.sport;
> > -		tuple.dst.u3.ip = bpf_tuple->ipv4.daddr;
> > -		tuple.dst.u.tcp.port = bpf_tuple->ipv4.dport;
> > +		tuple->src.l3num = AF_INET;
> > +		src->ip = bpf_tuple->ipv4.saddr;
> > +		sport->tcp.port = bpf_tuple->ipv4.sport;
> > +		dst->ip = bpf_tuple->ipv4.daddr;
> > +		dport->tcp.port = bpf_tuple->ipv4.dport;
> >  		break;
> >  	case sizeof(bpf_tuple->ipv6):
> > -		tuple.src.l3num = AF_INET6;
> > -		memcpy(tuple.src.u3.ip6, bpf_tuple->ipv6.saddr, sizeof(bpf_tuple->ipv6.saddr));
> > -		tuple.src.u.tcp.port = bpf_tuple->ipv6.sport;
> > -		memcpy(tuple.dst.u3.ip6, bpf_tuple->ipv6.daddr, sizeof(bpf_tuple->ipv6.daddr));
> > -		tuple.dst.u.tcp.port = bpf_tuple->ipv6.dport;
> > +		tuple->src.l3num = AF_INET6;
> > +		memcpy(src->ip6, bpf_tuple->ipv6.saddr, sizeof(bpf_tuple->ipv6.saddr));
> > +		sport->tcp.port = bpf_tuple->ipv6.sport;
> > +		memcpy(dst->ip6, bpf_tuple->ipv6.daddr, sizeof(bpf_tuple->ipv6.daddr));
> > +		dport->tcp.port = bpf_tuple->ipv6.dport;
> >  		break;
> >  	default:
> > -		return ERR_PTR(-EAFNOSUPPORT);
> > +		return -EAFNOSUPPORT;
> >  	}
> > +	tuple->dst.protonum = protonum;
> > +	tuple->dst.dir = dir;
> > +
> > +	return 0;
> > +}
> >  
> > -	tuple.dst.protonum = protonum;
> > +struct nf_conn *
> > +__bpf_nf_ct_alloc_entry(struct net *net, struct bpf_sock_tuple *bpf_tuple,
> > +			u32 tuple_len, u8 protonum, s32 netns_id, u32 timeout)
> > +{
> > +	struct nf_conntrack_tuple otuple, rtuple;
> > +	struct nf_conn *ct;
> > +	int err;
> > +
> > +	if (unlikely(netns_id < BPF_F_CURRENT_NETNS))
> > +		return ERR_PTR(-EINVAL);
> > +
> > +	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, protonum,
> > +				    IP_CT_DIR_ORIGINAL, &otuple);
> > +	if (err < 0)
> > +		return ERR_PTR(err);
> > +
> > +	err = bpf_nf_ct_tuple_parse(bpf_tuple, tuple_len, protonum,
> > +				    IP_CT_DIR_REPLY, &rtuple);
> > +	if (err < 0)
> > +		return ERR_PTR(err);
> > +
> > +	if (netns_id >= 0) {
> > +		net = get_net_ns_by_id(net, netns_id);
> > +		if (unlikely(!net))
> > +			return ERR_PTR(-ENONET);
> > +	}
> > +
> > +	ct = nf_conntrack_alloc(net, &nf_ct_zone_dflt, &otuple, &rtuple,
> > +				GFP_ATOMIC);
> > +	if (IS_ERR(ct))
> > +		goto out;
> > +
> > +	ct->timeout = timeout * HZ + jiffies;
> > +	ct->status |= IPS_CONFIRMED;
> > +
> > +	memset(&ct->proto, 0, sizeof(ct->proto));
> > +	if (protonum == IPPROTO_TCP)
> > +		ct->proto.tcp.state = TCP_CONNTRACK_ESTABLISHED;
> 
> Hmm, isn't it a bit limiting to hard-code this to ESTABLISHED
> connections? Presumably for TCP you'd want to use this when you see a
> SYN and then rely on conntrack to help with the subsequent state
> tracking for when the SYN-ACK comes back? What's the usecase for
> creating an entry in ESTABLISHED state, exactly?

I guess we can even add a parameter and pass the state from the caller.
I was not sure if it is mandatory.

Regards,
Lorenzo

> 
> (Of course, we'd need to be able to update the state as well, then...)
> 
> -Toke
> 

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