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Date: Mon, 20 May 2024 18:41:21 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: bpf <bpf@...r.kernel.org>, Pablo Neira Ayuso <pablo@...filter.org>,
Jozsef Kadlecsik <kadlec@...filter.org>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
netfilter-devel <netfilter-devel@...r.kernel.org>,
Network Development <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
Lorenzo Bianconi <lorenzo.bianconi@...hat.com>, Toke Høiland-Jørgensen <toke@...hat.com>,
Florian Westphal <fw@...len.de>, Jesper Dangaard Brouer <hawk@...nel.org>, Simon Horman <horms@...nel.org>, donhunte@...hat.com,
Kumar Kartikeya Dwivedi <memxor@...il.com>
Subject: Re: [PATCH bpf-next v2 2/4] netfilter: add bpf_xdp_flow_offload_lookup
kfunc
On Sat, May 18, 2024 at 3:13 AM Lorenzo Bianconi <lorenzo@...nel.org> wrote:
>
> Introduce bpf_xdp_flow_offload_lookup kfunc in order to perform the
> lookup of a given flowtable entry based on a fib tuple of incoming
> traffic.
> bpf_xdp_flow_offload_lookup can be used as building block to offload
> in xdp the processing of sw flowtable when hw flowtable is not
> available.
>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
> include/net/netfilter/nf_flow_table.h | 10 +++
> net/netfilter/Makefile | 5 ++
> net/netfilter/nf_flow_table_bpf.c | 94 +++++++++++++++++++++++++++
> net/netfilter/nf_flow_table_inet.c | 2 +-
> 4 files changed, 110 insertions(+), 1 deletion(-)
> create mode 100644 net/netfilter/nf_flow_table_bpf.c
>
> diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
> index 0bbe6ea8e0651..085660cbcd3f2 100644
> --- a/include/net/netfilter/nf_flow_table.h
> +++ b/include/net/netfilter/nf_flow_table.h
> @@ -312,6 +312,16 @@ unsigned int nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
> unsigned int nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
> const struct nf_hook_state *state);
>
> +#if (IS_BUILTIN(CONFIG_NF_FLOW_TABLE) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) || \
> + (IS_MODULE(CONFIG_NF_FLOW_TABLE) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
> +extern int nf_flow_offload_register_bpf(void);
> +#else
> +static inline int nf_flow_offload_register_bpf(void)
> +{
> + return 0;
> +}
> +#endif
> +
> #define MODULE_ALIAS_NF_FLOWTABLE(family) \
> MODULE_ALIAS("nf-flowtable-" __stringify(family))
>
> diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
> index 614815a3ed738..18b09cec92024 100644
> --- a/net/netfilter/Makefile
> +++ b/net/netfilter/Makefile
> @@ -144,6 +144,11 @@ obj-$(CONFIG_NF_FLOW_TABLE) += nf_flow_table.o
> nf_flow_table-objs := nf_flow_table_core.o nf_flow_table_ip.o \
> nf_flow_table_offload.o
> nf_flow_table-$(CONFIG_NF_FLOW_TABLE_PROCFS) += nf_flow_table_procfs.o
> +ifeq ($(CONFIG_NF_FLOW_TABLE),m)
> +nf_flow_table-$(CONFIG_DEBUG_INFO_BTF_MODULES) += nf_flow_table_bpf.o
> +else ifeq ($(CONFIG_NF_FLOW_TABLE),y)
> +nf_flow_table-$(CONFIG_DEBUG_INFO_BTF) += nf_flow_table_bpf.o
> +endif
>
> obj-$(CONFIG_NF_FLOW_TABLE_INET) += nf_flow_table_inet.o
>
> diff --git a/net/netfilter/nf_flow_table_bpf.c b/net/netfilter/nf_flow_table_bpf.c
> new file mode 100644
> index 0000000000000..f999ed9712796
> --- /dev/null
> +++ b/net/netfilter/nf_flow_table_bpf.c
> @@ -0,0 +1,94 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Unstable Flow Table Helpers for XDP hook
> + *
> + * These are called from the XDP programs.
> + * Note that it is allowed to break compatibility for these functions since
> + * the interface they are exposed through to BPF programs is explicitly
> + * unstable.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <net/netfilter/nf_flow_table.h>
> +#include <linux/bpf.h>
> +#include <linux/btf.h>
> +#include <net/xdp.h>
> +
> +__diag_push();
> +__diag_ignore_all("-Wmissing-prototypes",
> + "Global functions as their definitions will be in nf_flow_table BTF");
> +
> +static struct flow_offload_tuple_rhash *
> +bpf_xdp_flow_offload_tuple_lookup(struct net_device *dev,
> + struct flow_offload_tuple *tuple,
> + __be16 proto)
> +{
> + struct flow_offload_tuple_rhash *tuplehash;
> + struct nf_flowtable *flow_table;
> + struct flow_offload *flow;
> +
> + flow_table = nf_flowtable_by_dev(dev);
> + if (!flow_table)
> + return NULL;
> +
> + tuplehash = flow_offload_lookup(flow_table, tuple);
> + if (!tuplehash)
> + return NULL;
> +
> + flow = container_of(tuplehash, struct flow_offload,
> + tuplehash[tuplehash->tuple.dir]);
> + flow_offload_refresh(flow_table, flow, false);
> +
> + return tuplehash;
> +}
> +
> +__bpf_kfunc struct flow_offload_tuple_rhash *
> +bpf_xdp_flow_offload_lookup(struct xdp_md *ctx,
> + struct bpf_fib_lookup *fib_tuple)
> +{
> + struct xdp_buff *xdp = (struct xdp_buff *)ctx;
> + struct flow_offload_tuple tuple = {
> + .iifidx = fib_tuple->ifindex,
> + .l3proto = fib_tuple->family,
> + .l4proto = fib_tuple->l4_protocol,
> + .src_port = fib_tuple->sport,
> + .dst_port = fib_tuple->dport,
> + };
> + __be16 proto;
> +
> + switch (fib_tuple->family) {
> + case AF_INET:
> + tuple.src_v4.s_addr = fib_tuple->ipv4_src;
> + tuple.dst_v4.s_addr = fib_tuple->ipv4_dst;
> + proto = htons(ETH_P_IP);
> + break;
> + case AF_INET6:
> + tuple.src_v6 = *(struct in6_addr *)&fib_tuple->ipv6_src;
> + tuple.dst_v6 = *(struct in6_addr *)&fib_tuple->ipv6_dst;
> + proto = htons(ETH_P_IPV6);
> + break;
> + default:
> + return NULL;
> + }
> +
> + return bpf_xdp_flow_offload_tuple_lookup(xdp->rxq->dev, &tuple, proto);
> +}
> +
> +__diag_pop()
> +
> +BTF_KFUNCS_START(nf_ft_kfunc_set)
> +BTF_ID_FLAGS(func, bpf_xdp_flow_offload_lookup)
I think it needs to be KF_RET_NULL.
And most likely KF_TRUSTED_ARGS as well.
Also the "offload" doesn't fit in the name.
The existing code calls it "offload", because it's actually
pushing the rules to HW (if I understand the code),
but here it's just a lookup from xdp.
So call it
bpf_xdp_flow_lookup() ?
Though "flow" is a bit too generic here.
nf_flow maybe?
> +BTF_KFUNCS_END(nf_ft_kfunc_set)
> +
> +static const struct btf_kfunc_id_set nf_flow_offload_kfunc_set = {
> + .owner = THIS_MODULE,
> + .set = &nf_ft_kfunc_set,
> +};
> +
> +int nf_flow_offload_register_bpf(void)
> +{
> + return register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP,
> + &nf_flow_offload_kfunc_set);
> +}
> +EXPORT_SYMBOL_GPL(nf_flow_offload_register_bpf);
> diff --git a/net/netfilter/nf_flow_table_inet.c b/net/netfilter/nf_flow_table_inet.c
> index 6eef15648b7b0..6175f7556919d 100644
> --- a/net/netfilter/nf_flow_table_inet.c
> +++ b/net/netfilter/nf_flow_table_inet.c
> @@ -98,7 +98,7 @@ static int __init nf_flow_inet_module_init(void)
> nft_register_flowtable_type(&flowtable_ipv6);
> nft_register_flowtable_type(&flowtable_inet);
>
> - return 0;
> + return nf_flow_offload_register_bpf();
> }
>
> static void __exit nf_flow_inet_module_exit(void)
> --
> 2.45.1
>
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