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Message-ID: <0e72fb5b-2e26-4c28-b139-68203cd72e59@linux.dev>
Date: Sat, 25 Nov 2023 12:36:29 -0800
From: Yonghong Song <yonghong.song@...ux.dev>
To: Daniel Xu <dxu@...uu.xyz>, john.fastabend@...il.com,
Herbert Xu <herbert@...dor.apana.org.au>, davem@...emloft.net,
ast@...nel.org, daniel@...earbox.net, pabeni@...hat.com, hawk@...nel.org,
kuba@...nel.org, edumazet@...gle.com, steffen.klassert@...unet.com,
antony.antony@...unet.com, alexei.starovoitov@...il.com
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
bpf@...r.kernel.org, devel@...ux-ipsec.org
Subject: Re: [PATCH ipsec-next v1 1/7] bpf: xfrm: Add bpf_xdp_get_xfrm_state()
kfunc
On 11/22/23 1:20 PM, Daniel Xu wrote:
> This commit adds an unstable kfunc helper to access internal xfrm_state
> associated with an SA. This is intended to be used for the upcoming
> IPsec pcpu work to assign special pcpu SAs to a particular CPU. In other
> words: for custom software RSS.
>
> That being said, the function that this kfunc wraps is fairly generic
> and used for a lot of xfrm tasks. I'm sure people will find uses
> elsewhere over time.
>
> Co-developed-by: Antony Antony <antony.antony@...unet.com>
> Signed-off-by: Antony Antony <antony.antony@...unet.com>
> Signed-off-by: Daniel Xu <dxu@...uu.xyz>
> ---
> include/net/xfrm.h | 9 ++++
> net/xfrm/Makefile | 1 +
> net/xfrm/xfrm_policy.c | 2 +
> net/xfrm/xfrm_state_bpf.c | 111 ++++++++++++++++++++++++++++++++++++++
> 4 files changed, 123 insertions(+)
> create mode 100644 net/xfrm/xfrm_state_bpf.c
>
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index c9bb0f892f55..1d107241b901 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -2190,4 +2190,13 @@ static inline int register_xfrm_interface_bpf(void)
>
> #endif
>
> +#if IS_ENABLED(CONFIG_DEBUG_INFO_BTF)
> +int register_xfrm_state_bpf(void);
> +#else
> +static inline int register_xfrm_state_bpf(void)
> +{
> + return 0;
> +}
> +#endif
> +
> #endif /* _NET_XFRM_H */
> diff --git a/net/xfrm/Makefile b/net/xfrm/Makefile
> index cd47f88921f5..547cec77ba03 100644
> --- a/net/xfrm/Makefile
> +++ b/net/xfrm/Makefile
> @@ -21,3 +21,4 @@ obj-$(CONFIG_XFRM_USER_COMPAT) += xfrm_compat.o
> obj-$(CONFIG_XFRM_IPCOMP) += xfrm_ipcomp.o
> obj-$(CONFIG_XFRM_INTERFACE) += xfrm_interface.o
> obj-$(CONFIG_XFRM_ESPINTCP) += espintcp.o
> +obj-$(CONFIG_DEBUG_INFO_BTF) += xfrm_state_bpf.o
> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index c13dc3ef7910..1b7e75159727 100644
> --- a/net/xfrm/xfrm_policy.c
> +++ b/net/xfrm/xfrm_policy.c
> @@ -4218,6 +4218,8 @@ void __init xfrm_init(void)
> #ifdef CONFIG_XFRM_ESPINTCP
> espintcp_init();
> #endif
> +
> + register_xfrm_state_bpf();
> }
>
> #ifdef CONFIG_AUDITSYSCALL
> diff --git a/net/xfrm/xfrm_state_bpf.c b/net/xfrm/xfrm_state_bpf.c
> new file mode 100644
> index 000000000000..0c1f2f91125c
> --- /dev/null
> +++ b/net/xfrm/xfrm_state_bpf.c
> @@ -0,0 +1,111 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Unstable XFRM state BPF helpers.
> + *
> + * 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/bpf.h>
> +#include <linux/btf_ids.h>
> +#include <net/xdp.h>
> +#include <net/xfrm.h>
> +
> +/* bpf_xfrm_state_opts - Options for XFRM state lookup helpers
> + *
> + * Members:
> + * @error - Out parameter, set for any errors encountered
> + * Values:
> + * -EINVAL - netns_id is less than -1
> + * -EINVAL - Passed NULL for opts
> + * -EINVAL - opts__sz isn't BPF_XFRM_STATE_OPTS_SZ
> + * -ENONET - No network namespace found for netns_id
> + * @netns_id - Specify the network namespace for lookup
> + * Values:
> + * BPF_F_CURRENT_NETNS (-1)
> + * Use namespace associated with ctx
> + * [0, S32_MAX]
> + * Network Namespace ID
> + * @mark - XFRM mark to match on
> + * @daddr - Destination address to match on
> + * @spi - Security parameter index to match on
> + * @proto - L3 protocol to match on
> + * @family - L3 protocol family to match on
> + */
> +struct bpf_xfrm_state_opts {
> + s32 error;
> + s32 netns_id;
> + u32 mark;
> + xfrm_address_t daddr;
> + __be32 spi;
> + u8 proto;
> + u16 family;
> +};
> +
> +enum {
> + BPF_XFRM_STATE_OPTS_SZ = sizeof(struct bpf_xfrm_state_opts),
> +};
> +
> +__diag_push();
> +__diag_ignore_all("-Wmissing-prototypes",
> + "Global functions as their definitions will be in xfrm_state BTF");
> +
> +/* bpf_xdp_get_xfrm_state - Get XFRM state
> + *
> + * Parameters:
> + * @ctx - Pointer to ctx (xdp_md) in XDP program
> + * Cannot be NULL
> + * @opts - Options for lookup (documented above)
> + * Cannot be NULL
> + * @opts__sz - Length of the bpf_xfrm_state_opts structure
> + * Must be BPF_XFRM_STATE_OPTS_SZ
> + */
> +__bpf_kfunc struct xfrm_state *
> +bpf_xdp_get_xfrm_state(struct xdp_md *ctx, struct bpf_xfrm_state_opts *opts, u32 opts__sz)
> +{
> + struct xdp_buff *xdp = (struct xdp_buff *)ctx;
> + struct net *net = dev_net(xdp->rxq->dev);
> + struct xfrm_state *x;
> +
> + if (!opts || opts__sz != BPF_XFRM_STATE_OPTS_SZ) {
> + opts->error = -EINVAL;
If opts is NULL, obvious we have issue opts->error access.
If opts is not NULL and opts_sz < 4, we also have issue with
opts->error access since it may override some other stuff
on the stack.
In such cases, we do not need to do 'opts->error = -EINVAL'
and can simply 'return NULL'. bpf program won't be able
to check opts->error anyway since the opts is either NULL
or opts_sz < 4.
> + return NULL;
> + }
> +
> + if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS)) {
> + opts->error = -EINVAL;
> + return NULL;
> + }
> +
> + if (opts->netns_id >= 0) {
> + net = get_net_ns_by_id(net, opts->netns_id);
> + if (unlikely(!net)) {
> + opts->error = -ENONET;
> + return NULL;
> + }
> + }
> +
> + x = xfrm_state_lookup(net, opts->mark, &opts->daddr, opts->spi,
> + opts->proto, opts->family);
> +
> + if (opts->netns_id >= 0)
> + put_net(net);
> +
> + return x;
> +}
> +
> +__diag_pop()
[...]
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