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Date: Fri, 14 Jun 2024 00:34:21 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: pablo@...filter.org
Cc: bpf@...r.kernel.org, kadlec@...filter.org, davem@...emloft.net,
edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
martin.lau@...ux.dev, eddyz87@...il.com,
lorenzo.bianconi@...hat.com, toke@...hat.com, fw@...len.de,
hawk@...nel.org, horms@...nel.org, donhunte@...hat.com,
memxor@...il.com
Subject: Re: [PATCH v4 bpf-next 1/3] netfilter: nf_tables: add flowtable map
for xdp offload
> From: Florian Westphal <fw@...len.de>
>
> This adds a small internal mapping table so that a new bpf (xdp) kfunc
> can perform lookups in a flowtable.
>
> As-is, xdp program has access to the device pointer, but no way to do a
> lookup in a flowtable -- there is no way to obtain the needed struct
> without questionable stunts.
>
> This allows to obtain an nf_flowtable pointer given a net_device
> structure.
>
> In order to keep backward compatibility, the infrastructure allows the
> user to add a given device to multiple flowtables, but it will always
> return the first added mapping performing the lookup since it assumes
> the right configuration is 1:1 mapping between flowtables and net_devices.
Hi Pablo,
do you have any feedback about nft part? Thanks.
Regards,
Lorenzo
>
> Signed-off-by: Florian Westphal <fw@...len.de>
> Co-developed-by: Lorenzo Bianconi <lorenzo@...nel.org>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
> include/net/netfilter/nf_flow_table.h | 8 ++
> net/netfilter/Makefile | 2 +-
> net/netfilter/nf_flow_table_offload.c | 6 +-
> net/netfilter/nf_flow_table_xdp.c | 163 ++++++++++++++++++++++++++
> 4 files changed, 176 insertions(+), 3 deletions(-)
> create mode 100644 net/netfilter/nf_flow_table_xdp.c
>
> diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
> index 9abb7ee40d72f..688e02b287cc4 100644
> --- a/include/net/netfilter/nf_flow_table.h
> +++ b/include/net/netfilter/nf_flow_table.h
> @@ -305,6 +305,14 @@ struct flow_ports {
> __be16 source, dest;
> };
>
> +struct nf_flowtable *nf_flowtable_by_dev(const struct net_device *dev);
> +int nf_flow_offload_xdp_setup(struct nf_flowtable *flowtable,
> + struct net_device *dev,
> + enum flow_block_command cmd);
> +void nf_flow_offload_xdp_cancel(struct nf_flowtable *flowtable,
> + struct net_device *dev,
> + enum flow_block_command cmd);
> +
> unsigned int nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
> const struct nf_hook_state *state);
> unsigned int nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
> diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
> index 614815a3ed738..18046872a38aa 100644
> --- a/net/netfilter/Makefile
> +++ b/net/netfilter/Makefile
> @@ -142,7 +142,7 @@ obj-$(CONFIG_NFT_FWD_NETDEV) += nft_fwd_netdev.o
> # flow table infrastructure
> obj-$(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_offload.o nf_flow_table_xdp.o
> nf_flow_table-$(CONFIG_NF_FLOW_TABLE_PROCFS) += nf_flow_table_procfs.o
>
> obj-$(CONFIG_NF_FLOW_TABLE_INET) += nf_flow_table_inet.o
> diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
> index a010b25076ca0..d9b019c98694b 100644
> --- a/net/netfilter/nf_flow_table_offload.c
> +++ b/net/netfilter/nf_flow_table_offload.c
> @@ -1192,7 +1192,7 @@ int nf_flow_table_offload_setup(struct nf_flowtable *flowtable,
> int err;
>
> if (!nf_flowtable_hw_offload(flowtable))
> - return 0;
> + return nf_flow_offload_xdp_setup(flowtable, dev, cmd);
>
> if (dev->netdev_ops->ndo_setup_tc)
> err = nf_flow_table_offload_cmd(&bo, flowtable, dev, cmd,
> @@ -1200,8 +1200,10 @@ int nf_flow_table_offload_setup(struct nf_flowtable *flowtable,
> else
> err = nf_flow_table_indr_offload_cmd(&bo, flowtable, dev, cmd,
> &extack);
> - if (err < 0)
> + if (err < 0) {
> + nf_flow_offload_xdp_cancel(flowtable, dev, cmd);
> return err;
> + }
>
> return nf_flow_table_block_setup(flowtable, &bo, cmd);
> }
> diff --git a/net/netfilter/nf_flow_table_xdp.c b/net/netfilter/nf_flow_table_xdp.c
> new file mode 100644
> index 0000000000000..b9bdf27ba9bd3
> --- /dev/null
> +++ b/net/netfilter/nf_flow_table_xdp.c
> @@ -0,0 +1,163 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/netfilter.h>
> +#include <linux/rhashtable.h>
> +#include <linux/netdevice.h>
> +#include <net/flow_offload.h>
> +#include <net/netfilter/nf_flow_table.h>
> +
> +struct flow_offload_xdp_ft {
> + struct list_head head;
> + struct nf_flowtable *ft;
> + struct rcu_head rcuhead;
> +};
> +
> +struct flow_offload_xdp {
> + struct hlist_node hnode;
> + unsigned long net_device_addr;
> + struct list_head head;
> +};
> +
> +#define NF_XDP_HT_BITS 4
> +static DEFINE_HASHTABLE(nf_xdp_hashtable, NF_XDP_HT_BITS);
> +static DEFINE_MUTEX(nf_xdp_hashtable_lock);
> +
> +/* caller must hold rcu read lock */
> +struct nf_flowtable *nf_flowtable_by_dev(const struct net_device *dev)
> +{
> + unsigned long key = (unsigned long)dev;
> + struct flow_offload_xdp *iter;
> +
> + hash_for_each_possible_rcu(nf_xdp_hashtable, iter, hnode, key) {
> + if (key == iter->net_device_addr) {
> + struct flow_offload_xdp_ft *ft_elem;
> +
> + /* The user is supposed to insert a given net_device
> + * just into a single nf_flowtable so we always return
> + * the first element here.
> + */
> + ft_elem = list_first_or_null_rcu(&iter->head,
> + struct flow_offload_xdp_ft,
> + head);
> + return ft_elem ? ft_elem->ft : NULL;
> + }
> + }
> +
> + return NULL;
> +}
> +
> +static int nf_flowtable_by_dev_insert(struct nf_flowtable *ft,
> + const struct net_device *dev)
> +{
> + struct flow_offload_xdp *iter, *elem = NULL;
> + unsigned long key = (unsigned long)dev;
> + struct flow_offload_xdp_ft *ft_elem;
> +
> + ft_elem = kzalloc(sizeof(*ft_elem), GFP_KERNEL_ACCOUNT);
> + if (!ft_elem)
> + return -ENOMEM;
> +
> + ft_elem->ft = ft;
> +
> + mutex_lock(&nf_xdp_hashtable_lock);
> +
> + hash_for_each_possible(nf_xdp_hashtable, iter, hnode, key) {
> + if (key == iter->net_device_addr) {
> + elem = iter;
> + break;
> + }
> + }
> +
> + if (!elem) {
> + elem = kzalloc(sizeof(*elem), GFP_KERNEL_ACCOUNT);
> + if (!elem)
> + goto err_unlock;
> +
> + elem->net_device_addr = key;
> + INIT_LIST_HEAD(&elem->head);
> + hash_add_rcu(nf_xdp_hashtable, &elem->hnode, key);
> + }
> + list_add_tail_rcu(&ft_elem->head, &elem->head);
> +
> + mutex_unlock(&nf_xdp_hashtable_lock);
> +
> + return 0;
> +
> +err_unlock:
> + mutex_unlock(&nf_xdp_hashtable_lock);
> + kfree(ft_elem);
> +
> + return -ENOMEM;
> +}
> +
> +static void nf_flowtable_by_dev_remove(struct nf_flowtable *ft,
> + const struct net_device *dev)
> +{
> + struct flow_offload_xdp *iter, *elem = NULL;
> + unsigned long key = (unsigned long)dev;
> +
> + mutex_lock(&nf_xdp_hashtable_lock);
> +
> + hash_for_each_possible(nf_xdp_hashtable, iter, hnode, key) {
> + if (key == iter->net_device_addr) {
> + elem = iter;
> + break;
> + }
> + }
> +
> + if (elem) {
> + struct flow_offload_xdp_ft *ft_elem, *ft_next;
> +
> + list_for_each_entry_safe(ft_elem, ft_next, &elem->head, head) {
> + if (ft_elem->ft == ft) {
> + list_del_rcu(&ft_elem->head);
> + kfree_rcu(ft_elem, rcuhead);
> + }
> + }
> +
> + if (list_empty(&elem->head))
> + hash_del_rcu(&elem->hnode);
> + else
> + elem = NULL;
> + }
> +
> + mutex_unlock(&nf_xdp_hashtable_lock);
> +
> + if (elem) {
> + synchronize_rcu();
> + kfree(elem);
> + }
> +}
> +
> +int nf_flow_offload_xdp_setup(struct nf_flowtable *flowtable,
> + struct net_device *dev,
> + enum flow_block_command cmd)
> +{
> + switch (cmd) {
> + case FLOW_BLOCK_BIND:
> + return nf_flowtable_by_dev_insert(flowtable, dev);
> + case FLOW_BLOCK_UNBIND:
> + nf_flowtable_by_dev_remove(flowtable, dev);
> + return 0;
> + }
> +
> + WARN_ON_ONCE(1);
> + return 0;
> +}
> +
> +void nf_flow_offload_xdp_cancel(struct nf_flowtable *flowtable,
> + struct net_device *dev,
> + enum flow_block_command cmd)
> +{
> + switch (cmd) {
> + case FLOW_BLOCK_BIND:
> + nf_flowtable_by_dev_remove(flowtable, dev);
> + return;
> + case FLOW_BLOCK_UNBIND:
> + /* We do not re-bind in case hw offload would report error
> + * on *unregister*.
> + */
> + break;
> + }
> +}
> --
> 2.45.1
>
>
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