This commit introduces a helper which allows fetching xfrm state
parameters by eBPF programs attached to TC.
Prototype:
bpf_skb_get_xfrm_state(skb, index, xfrm_state, size, flags)
skb: pointer to skb
index: the index in the skb xfrm_state secpath array
xfrm_state: pointer to 'struct bpf_xfrm_state'
size: size of 'struct bpf_xfrm_state'
flags: reserved for future extensions
The helper returns 0 on success. Non zero if no xfrm state at the index
is found - or non exists at all.
struct bpf_xfrm_state currently includes the SPI, peer IPv4/IPv6
address and the reqid; it can be further extended by adding elements to
its end - indicating the populated fields by the 'size' argument -
keeping backwards compatibility.
Typical usage:
struct bpf_xfrm_state x = {};
bpf_skb_get_xfrm_state(skb, 0, &x, sizeof(x), 0);
...
Signed-off-by: Eyal Birger <eyal.bir...@gmail.com>
---
include/uapi/linux/bpf.h | 25 ++++++++++++++++++++++++-
net/core/filter.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 70 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c5ec897..132e172 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -755,6 +755,15 @@ union bpf_attr {
* @addr: pointer to struct sockaddr to bind socket to
* @addr_len: length of sockaddr structure
* Return: 0 on success or negative error code
+ *
+ * int bpf_skb_get_xfrm_state(skb, index, xfrm_state, size, flags)
+ * retrieve XFRM state
+ * @skb: pointer to skb
+ * @index: index of the xfrm state in the secpath
+ * @key: pointer to 'struct bpf_xfrm_state'
+ * @size: size of 'struct bpf_xfrm_state'
+ * @flags: room for future extensions
+ * Return: 0 on success or negative error
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -821,7 +830,8 @@ union bpf_attr {
FN(msg_apply_bytes), \
FN(msg_cork_bytes), \
FN(msg_pull_data), \
- FN(bind),
+ FN(bind), \
+ FN(skb_get_xfrm_state),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -927,6 +937,19 @@ struct bpf_tunnel_key {
__u32 tunnel_label;
};
+/* user accessible mirror of in-kernel xfrm_state.
+ * new fields can only be added to the end of this structure
+ */
+struct bpf_xfrm_state {
+ __u32 reqid;
+ __u32 spi;
+ __u16 family;
+ union {
+ __u32 remote_ipv4;
+ __u32 remote_ipv6[4];
+ };
+};
+
/* Generic BPF return codes which all BPF program types may support.
* The values are binary compatible with their TC_ACT_* counter-part to
* provide backwards compatibility with existing SCHED_CLS and SCHED_ACT
diff --git a/net/core/filter.c b/net/core/filter.c
index d31aff9..c06600a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -57,6 +57,7 @@
#include <net/sock_reuseport.h>
#include <net/busy_poll.h>
#include <net/tcp.h>
+#include <net/xfrm.h>
#include <linux/bpf_trace.h>
/**
@@ -3703,6 +3704,49 @@ static const struct bpf_func_proto bpf_bind_proto = {
.arg3_type = ARG_CONST_SIZE,
};
+BPF_CALL_5(bpf_skb_get_xfrm_state, struct sk_buff *, skb, u32, index,
+ struct bpf_xfrm_state *, to, u32, size, u64, flags)
+{
+#ifdef CONFIG_XFRM
+ const struct sec_path *sp = skb_sec_path(skb);
+ const struct xfrm_state *x;
+
+ if (!sp || index >= sp->len)
+ goto err_clear;
+
+ x = sp->xvec[index];
+
+ if (unlikely(size != sizeof(struct bpf_xfrm_state)))
+ goto err_clear;
+
+ to->reqid = x->props.reqid;
+ to->spi = be32_to_cpu(x->id.spi);
+ to->family = x->props.family;
+ if (to->family == AF_INET6) {
+ memcpy(to->remote_ipv6, x->props.saddr.a6,
+ sizeof(to->remote_ipv6));
+ } else {
+ to->remote_ipv4 = be32_to_cpu(x->props.saddr.a4);
+ }
+
+ return 0;
+err_clear:
+#endif
+ memset(to, 0, size);
+ return -EINVAL;
+}
+
+static const struct bpf_func_proto bpf_skb_get_xfrm_state_proto = {
+ .func = bpf_skb_get_xfrm_state,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg4_type = ARG_CONST_SIZE,
+ .arg5_type = ARG_ANYTHING,
+};
+
static const struct bpf_func_proto *
bpf_base_func_proto(enum bpf_func_id func_id)
{
@@ -3844,6 +3888,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const
struct bpf_prog *prog)
return &bpf_get_socket_cookie_proto;
case BPF_FUNC_get_socket_uid:
return &bpf_get_socket_uid_proto;
+ case BPF_FUNC_skb_get_xfrm_state:
+ return &bpf_skb_get_xfrm_state_proto;
default:
return bpf_base_func_proto(func_id);
}
--
2.7.4
