[PATCH ipsec-next v3 1/9] bpf: xfrm: Add bpf_xdp_get_xfrm_state() kfunc

Daniel Xu
2023-12-01T20:23:58Z

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@secunet.com>
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
include/net/xfrm.h | 9 +++
net/xfrm/Makefile | 1 +
net/xfrm/xfrm_policy.c | 2 +
net/xfrm/xfrm_state_bpf.c | 112 ++++++++++++++++++++++++++++++++++++++
4 files changed, 124 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..1681825db506
--- /dev/null
+++ b/net/xfrm/xfrm_state_bpf.c
@@ -0,0 +1,112 @@
+// 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.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 - 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),
+};
+
+__bpf_kfunc_start_defs();
+
+/* 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 < sizeof(opts->error))
+ return NULL;
+
+ if (opts__sz != BPF_XFRM_STATE_OPTS_SZ) {
+ opts->error = -EINVAL;
+ 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;
+}
+
+__bpf_kfunc_end_defs();
+
+BTF_SET8_START(xfrm_state_kfunc_set)
+BTF_ID_FLAGS(func, bpf_xdp_get_xfrm_state, KF_RET_NULL | KF_ACQUIRE)
+BTF_SET8_END(xfrm_state_kfunc_set)
+
+static const struct btf_kfunc_id_set xfrm_state_xdp_kfunc_set = {
+ .owner = THIS_MODULE,
+ .set = &xfrm_state_kfunc_set,
+};
+
+int __init register_xfrm_state_bpf(void)
+{
+ return register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP,
+ &xfrm_state_xdp_kfunc_set);
+}
--
2.42.1