bpf: add helpers to access tunnel metadata

Introduce helpers to let eBPF programs attached to TC manipulate tunnel metadata:
bpf_skb_[gs]et_tunnel_key(skb, key, size, flags)
skb: pointer to skb
key: pointer to 'struct bpf_tunnel_key'
size: size of 'struct bpf_tunnel_key'
flags: room for future extensions

First eBPF program that uses these helpers will allocate per_cpu
metadata_dst structures that will be used on TX.
On RX metadata_dst is allocated by tunnel driver.

Typical usage for TX:
struct bpf_tunnel_key tkey;
... populate tkey ...
bpf_skb_set_tunnel_key(skb, &tkey, sizeof(tkey), 0);
bpf_clone_redirect(skb, vxlan_dev_ifindex, 0);

RX:
struct bpf_tunnel_key tkey = {};
bpf_skb_get_tunnel_key(skb, &tkey, sizeof(tkey), 0);
... lookup or redirect based on tkey ...

'struct bpf_tunnel_key' will be extended in the future by adding
elements to the end and the 'size' argument will indicate which fields
are populated, thereby keeping backwards compatibility.
The 'flags' argument may be used as well when the 'size' is not enough or
to indicate completely different layout of bpf_tunnel_key.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 6 deletions

diff --git a/net/core/dst.c b/net/core/dst.c
index 76a617f..f8694d1 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -362,15 +362,10 @@ static int dst_md_discard(struct sk_buff *skb)
 	return 0;
 }
 
-struct metadata_dst *metadata_dst_alloc(u8 optslen, gfp_t flags)
+static void __metadata_dst_init(struct metadata_dst *md_dst, u8 optslen)
 {
-	struct metadata_dst *md_dst;
 	struct dst_entry *dst;
 
-	md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
-	if (!md_dst)
-		return ERR_PTR(-ENOMEM);
-
 	dst = &md_dst->dst;
 	dst_init(dst, &md_dst_ops, NULL, 1, DST_OBSOLETE_NONE,
 		 DST_METADATA | DST_NOCACHE | DST_NOCOUNT);
@@ -380,11 +375,39 @@ struct metadata_dst *metadata_dst_alloc(u8 optslen, gfp_t flags)
 
 	memset(dst + 1, 0, sizeof(*md_dst) + optslen - sizeof(*dst));
 	md_dst->opts_len = optslen;
+}
+
+struct metadata_dst *metadata_dst_alloc(u8 optslen, gfp_t flags)
+{
+	struct metadata_dst *md_dst;
+
+	md_dst = kmalloc(sizeof(*md_dst) + optslen, flags);
+	if (!md_dst)
+		return NULL;
+
+	__metadata_dst_init(md_dst, optslen);
 
 	return md_dst;
 }
 EXPORT_SYMBOL_GPL(metadata_dst_alloc);
 
+struct metadata_dst __percpu *metadata_dst_alloc_percpu(u8 optslen, gfp_t flags)
+{
+	int cpu;
+	struct metadata_dst __percpu *md_dst;
+
+	md_dst = __alloc_percpu_gfp(sizeof(struct metadata_dst) + optslen,
+				    __alignof__(struct metadata_dst), flags);
+	if (!md_dst)
+		return NULL;
+
+	for_each_possible_cpu(cpu)
+		__metadata_dst_init(per_cpu_ptr(md_dst, cpu), optslen);
+
+	return md_dst;
+}
+EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);
+
 /* Dirty hack. We did it in 2.2 (in __dst_free),
  * we have _very_ good reasons not to repeat
  * this mistake in 2.3, but we have no choice