bpf: xfrm: Add bpf_xdp_get_xfrm_state() kfunc

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.

This commit also adds a corresponding bpf_xdp_xfrm_state_release() kfunc
to release the refcnt acquired by bpf_xdp_get_xfrm_state(). The verifier
will require that all acquired xfrm_state's are released.

Co-developed-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/a29699c42f5fad456b875c98dd11c6afc3ffb707.1702593901.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index c9bb0f892f55595bc41d1394104ff3d06a0d48bd..1d107241b9018798f32997f813d344561ef6fae6 100644 (file)
--- 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 cd47f88921f5975d71e258c58652ca0d8a46fe5f..547cec77ba03cb9b4059a0f5efdb7df31da81c0a 100644 (file)
--- 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 c13dc3ef791072186b7e906de4664bacc132ef53..1b7e75159727791ef5ed03299729711ed775a16e 100644 (file)
--- 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 (file)
index 0000000..9e20d4a
--- /dev/null
+++ b/net/xfrm/xfrm_state_bpf.c
@@ -0,0 +1,134 @@
+// 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
+ *                -ENOENT - No xfrm_state found
+ * @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      - IP protocol to match on (eg. IPPROTO_ESP)
+ * @family     - Protocol family to match on (AF_INET/AF_INET6)
+ */
+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
+ *
+ * A `struct xfrm_state *`, if found, must be released with a corresponding
+ * bpf_xdp_xfrm_state_release.
+ *
+ * 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);
+       if (!x)
+               opts->error = -ENOENT;
+
+       return x;
+}
+
+/* bpf_xdp_xfrm_state_release - Release acquired xfrm_state object
+ *
+ * This must be invoked for referenced PTR_TO_BTF_ID, and the verifier rejects
+ * the program if any references remain in the program in all of the explored
+ * states.
+ *
+ * Parameters:
+ * @x          - Pointer to referenced xfrm_state object, obtained using
+ *               bpf_xdp_get_xfrm_state.
+ */
+__bpf_kfunc void bpf_xdp_xfrm_state_release(struct xfrm_state *x)
+{
+       xfrm_state_put(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_ID_FLAGS(func, bpf_xdp_xfrm_state_release, KF_RELEASE)
+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);
+}