From 91bc4822c3d61b9bb7ef66d3b77948a4f9177954 Mon Sep 17 00:00:00 2001
From: Alexei Starovoitov <ast@plumgrid.com>
Date: Wed, 1 Apr 2015 17:12:13 -0700
Subject: tc: bpf: add checksum helpers
Commit 608cd71a9c7c ("tc: bpf: generalize pedit action") has added the
possibility to mangle packet data to BPF programs in the tc pipeline.
This patch adds two helpers bpf_l3_csum_replace() and bpf_l4_csum_replace()
for fixing up the protocol checksums after the packet mangling.
It also adds 'flags' argument to bpf_skb_store_bytes() helper to avoid
unnecessary checksum recomputations when BPF programs adjusting l3/l4
checksums and documents all three helpers in uapi header.
Moreover, a sample program is added to show how BPF programs can make use
of the mangle and csum helpers.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/core/filter.c | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 104 insertions(+), 4 deletions(-)
(limited to 'net')
diff --git a/net/core/filter.c b/net/core/filter.c
index 955a7d77decd..b669e75d2b36 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1175,7 +1175,9 @@ int sk_attach_bpf(u32 ufd, struct sock *sk)
return 0;
}
-static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+#define BPF_RECOMPUTE_CSUM(flags) ((flags) & 1)
+
+static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
{
struct sk_buff *skb = (struct sk_buff *) (long) r1;
unsigned int offset = (unsigned int) r2;
@@ -1192,7 +1194,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
*
* so check for invalid 'offset' and too large 'len'
*/
- if (offset > 0xffff || len > sizeof(buf))
+ if (unlikely(offset > 0xffff || len > sizeof(buf)))
return -EFAULT;
if (skb_cloned(skb) && !skb_clone_writable(skb, offset + len))
@@ -1202,7 +1204,8 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
if (unlikely(!ptr))
return -EFAULT;
- skb_postpull_rcsum(skb, ptr, len);
+ if (BPF_RECOMPUTE_CSUM(flags))
+ skb_postpull_rcsum(skb, ptr, len);
memcpy(ptr, from, len);
@@ -1210,7 +1213,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
/* skb_store_bits cannot return -EFAULT here */
skb_store_bits(skb, offset, ptr, len);
- if (skb->ip_summed == CHECKSUM_COMPLETE)
+ if (BPF_RECOMPUTE_CSUM(flags) && skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_add(skb->csum, csum_partial(ptr, len, 0));
return 0;
}
@@ -1223,6 +1226,99 @@ const struct bpf_func_proto bpf_skb_store_bytes_proto = {
.arg2_type = ARG_ANYTHING,
.arg3_type = ARG_PTR_TO_STACK,
.arg4_type = ARG_CONST_STACK_SIZE,
+ .arg5_type = ARG_ANYTHING,
+};
+
+#define BPF_HEADER_FIELD_SIZE(flags) ((flags) & 0x0f)
+#define BPF_IS_PSEUDO_HEADER(flags) ((flags) & 0x10)
+
+static u64 bpf_l3_csum_replace(u64 r1, u64 offset, u64 from, u64 to, u64 flags)
+{
+ struct sk_buff *skb = (struct sk_buff *) (long) r1;
+ __sum16 sum, *ptr;
+
+ if (unlikely(offset > 0xffff))
+ return -EFAULT;
+
+ if (skb_cloned(skb) && !skb_clone_writable(skb, offset + sizeof(sum)))
+ return -EFAULT;
+
+ ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
+ if (unlikely(!ptr))
+ return -EFAULT;
+
+ switch (BPF_HEADER_FIELD_SIZE(flags)) {
+ case 2:
+ csum_replace2(ptr, from, to);
+ break;
+ case 4:
+ csum_replace4(ptr, from, to);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (ptr == &sum)
+ /* skb_store_bits guaranteed to not return -EFAULT here */
+ skb_store_bits(skb, offset, ptr, sizeof(sum));
+
+ return 0;
+}
+
+const struct bpf_func_proto bpf_l3_csum_replace_proto = {
+ .func = bpf_l3_csum_replace,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_ANYTHING,
+ .arg5_type = ARG_ANYTHING,
+};
+
+static u64 bpf_l4_csum_replace(u64 r1, u64 offset, u64 from, u64 to, u64 flags)
+{
+ struct sk_buff *skb = (struct sk_buff *) (long) r1;
+ u32 is_pseudo = BPF_IS_PSEUDO_HEADER(flags);
+ __sum16 sum, *ptr;
+
+ if (unlikely(offset > 0xffff))
+ return -EFAULT;
+
+ if (skb_cloned(skb) && !skb_clone_writable(skb, offset + sizeof(sum)))
+ return -EFAULT;
+
+ ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
+ if (unlikely(!ptr))
+ return -EFAULT;
+
+ switch (BPF_HEADER_FIELD_SIZE(flags)) {
+ case 2:
+ inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);
+ break;
+ case 4:
+ inet_proto_csum_replace4(ptr, skb, from, to, is_pseudo);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (ptr == &sum)
+ /* skb_store_bits guaranteed to not return -EFAULT here */
+ skb_store_bits(skb, offset, ptr, sizeof(sum));
+
+ return 0;
+}
+
+const struct bpf_func_proto bpf_l4_csum_replace_proto = {
+ .func = bpf_l4_csum_replace,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_ANYTHING,
+ .arg5_type = ARG_ANYTHING,
};
static const struct bpf_func_proto *
@@ -1250,6 +1346,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
switch (func_id) {
case BPF_FUNC_skb_store_bytes:
return &bpf_skb_store_bytes_proto;
+ case BPF_FUNC_l3_csum_replace:
+ return &bpf_l3_csum_replace_proto;
+ case BPF_FUNC_l4_csum_replace:
+ return &bpf_l4_csum_replace_proto;
default:
return sk_filter_func_proto(func_id);
}
--
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