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Date: Wed, 18 May 2022 23:08:55 +0200
From: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
andrii@...nel.org, davem@...emloft.net, kuba@...nel.org,
edumazet@...gle.com, pabeni@...hat.com, pablo@...filter.org,
fw@...len.de, netfilter-devel@...r.kernel.org, brouer@...hat.com,
memxor@...il.com
Subject: Re: [PATCH v3 bpf-next 4/5] net: netfilter: add kfunc helper to add
a new ct entry
> Lorenzo Bianconi <lorenzo@...nel.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@...nel.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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