[PATCH bpf-next] bpf: add bpf_get_xdp_hash helper function
From: Harshitha Ramamurthy <hidden>
Date: 2020-08-31 19:28:18
This patch adds a helper function called bpf_get_xdp_hash to calculate the hash for a packet at the XDP layer. In the helper function, we call the kernel flow dissector in non-skb mode by passing the net pointer to calculate the hash. Changes since RFC: - accounted for vlans(David Ahern) - return the correct hash by not using skb_get_hash(David Ahern) - call __skb_flow_dissect in non-skb mode Signed-off-by: Harshitha Ramamurthy <redacted> --- include/uapi/linux/bpf.h | 9 +++++++++ net/core/filter.c | 29 +++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 9 +++++++++ 3 files changed, 47 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index a613750d5515..bffe93b526e7 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h@@ -3576,6 +3576,14 @@ union bpf_attr { * the data in *dst*. This is a wrapper of copy_from_user(). * Return * 0 on success, or a negative error in case of failure. + * + * u32 bpf_get_xdp_hash(struct xdp_buff *xdp_md) + * Description + * Return the hash for the xdp context passed. This function + * calls skb_flow_dissect in non-skb mode to calculate the + * hash for the packet. + * Return + * The 32-bit hash. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \
@@ -3727,6 +3735,7 @@ union bpf_attr { FN(inode_storage_delete), \ FN(d_path), \ FN(copy_from_user), \ + FN(get_xdp_hash), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/net/core/filter.c b/net/core/filter.c
index 47eef9a0be6a..cfb5a6aea6c3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c@@ -3765,6 +3765,33 @@ static const struct bpf_func_proto bpf_xdp_redirect_map_proto = { .arg3_type = ARG_ANYTHING, }; +BPF_CALL_1(bpf_get_xdp_hash, struct xdp_buff *, xdp) +{ + void *data_end = xdp->data_end; + struct ethhdr *eth = xdp->data; + void *data = xdp->data; + struct flow_keys keys; + u32 ret = 0; + int len; + + len = data_end - data; + if (len <= 0) + return ret; + memset(&keys, 0, sizeof(keys)); + __skb_flow_dissect(dev_net(xdp->rxq->dev), NULL, &flow_keys_dissector, + &keys, data, eth->h_proto, sizeof(*eth), len, + FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL); + ret = flow_hash_from_keys(&keys); + return ret; +} + +static const struct bpf_func_proto bpf_get_xdp_hash_proto = { + .func = bpf_get_xdp_hash, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, +}; + static unsigned long bpf_skb_copy(void *dst_buff, const void *skb, unsigned long off, unsigned long len) {
@@ -6837,6 +6864,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_xdp_adjust_tail_proto; case BPF_FUNC_fib_lookup: return &bpf_xdp_fib_lookup_proto; + case BPF_FUNC_get_xdp_hash: + return &bpf_get_xdp_hash_proto; #ifdef CONFIG_INET case BPF_FUNC_sk_lookup_udp: return &bpf_xdp_sk_lookup_udp_proto;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index a613750d5515..bffe93b526e7 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h@@ -3576,6 +3576,14 @@ union bpf_attr { * the data in *dst*. This is a wrapper of copy_from_user(). * Return * 0 on success, or a negative error in case of failure. + * + * u32 bpf_get_xdp_hash(struct xdp_buff *xdp_md) + * Description + * Return the hash for the xdp context passed. This function + * calls skb_flow_dissect in non-skb mode to calculate the + * hash for the packet. + * Return + * The 32-bit hash. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \
@@ -3727,6 +3735,7 @@ union bpf_attr { FN(inode_storage_delete), \ FN(d_path), \ FN(copy_from_user), \ + FN(get_xdp_hash), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper
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2.20.1