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Date: Mon, 16 Mar 2015 18:06:02 -0700
From: Alexei Starovoitov <ast@...mgrid.com>
To: "David S. Miller" <davem@...emloft.net>
Cc: Daniel Borkmann <daniel@...earbox.net>,
Thomas Graf <tgraf@...g.ch>, linux-api@...r.kernel.org,
netdev@...r.kernel.org
Subject: [PATCH net-next] bpf: allow BPF programs access 'protocol' and 'vlan_tci' fields
as a follow on to patch 70006af95515 ("bpf: allow eBPF access skb fields")
this patch allows 'protocol' and 'vlan_tci' fields to be accessible
from extended BPF programs.
The usage of 'protocol', 'vlan_present' and 'vlan_tci' fields is the same as
corresponding SKF_AD_PROTOCOL, SKF_AD_VLAN_TAG_PRESENT and SKF_AD_VLAN_TAG
accesses in classic BPF.
Signed-off-by: Alexei Starovoitov <ast@...mgrid.com>
---
1.
I was thinking to drop ntohs() from 'protocol' field for extended BPF, since
the programs could do:
if (skb->protocol == htons(ETH_P_IP))
which would have saved one or two cpu cycles.
But having similar behavior between classic and extended seems to be better.
2.
'vlan_tci' name is picked to match real sk_buff->vlan_tci field
and matches tpacket's tp_vlan_tci field.
include/uapi/linux/bpf.h | 3 ++
net/core/filter.c | 72 ++++++++++++++++++++++++++++++-------------
samples/bpf/test_verifier.c | 9 ++++++
3 files changed, 62 insertions(+), 22 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 929545a27546..1623047af463 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -178,6 +178,9 @@ struct __sk_buff {
__u32 pkt_type;
__u32 mark;
__u32 queue_mapping;
+ __u32 protocol;
+ __u32 vlan_present;
+ __u32 vlan_tci;
};
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/net/core/filter.c b/net/core/filter.c
index 4e9dd0ad0d5b..b95ae7fe7e4f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -177,6 +177,35 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
offsetof(struct sk_buff, queue_mapping));
break;
+
+ case SKF_AD_PROTOCOL:
+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
+
+ /* dst_reg = *(u16 *) (src_reg + offsetof(protocol)) */
+ *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
+ offsetof(struct sk_buff, protocol));
+ /* dst_reg = ntohs(dst_reg) [emitting a nop or swap16] */
+ *insn++ = BPF_ENDIAN(BPF_FROM_BE, dst_reg, 16);
+ break;
+
+ case SKF_AD_VLAN_TAG:
+ case SKF_AD_VLAN_TAG_PRESENT:
+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
+ BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
+
+ /* dst_reg = *(u16 *) (src_reg + offsetof(vlan_tci)) */
+ *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
+ offsetof(struct sk_buff, vlan_tci));
+ if (skb_field == SKF_AD_VLAN_TAG) {
+ *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg,
+ ~VLAN_TAG_PRESENT);
+ } else {
+ /* dst_reg >>= 12 */
+ *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 12);
+ /* dst_reg &= 1 */
+ *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
+ }
+ break;
}
return insn - insn_buf;
@@ -190,13 +219,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp,
switch (fp->k) {
case SKF_AD_OFF + SKF_AD_PROTOCOL:
- BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
-
- /* A = *(u16 *) (CTX + offsetof(protocol)) */
- *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
- offsetof(struct sk_buff, protocol));
- /* A = ntohs(A) [emitting a nop or swap16] */
- *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
+ cnt = convert_skb_access(SKF_AD_PROTOCOL, BPF_REG_A, BPF_REG_CTX, insn);
+ insn += cnt - 1;
break;
case SKF_AD_OFF + SKF_AD_PKTTYPE:
@@ -242,22 +266,15 @@ static bool convert_bpf_extensions(struct sock_filter *fp,
break;
case SKF_AD_OFF + SKF_AD_VLAN_TAG:
- case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
- BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
- BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
+ cnt = convert_skb_access(SKF_AD_VLAN_TAG,
+ BPF_REG_A, BPF_REG_CTX, insn);
+ insn += cnt - 1;
+ break;
- /* A = *(u16 *) (CTX + offsetof(vlan_tci)) */
- *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
- offsetof(struct sk_buff, vlan_tci));
- if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {
- *insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A,
- ~VLAN_TAG_PRESENT);
- } else {
- /* A >>= 12 */
- *insn++ = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 12);
- /* A &= 1 */
- *insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 1);
- }
+ case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
+ cnt = convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,
+ BPF_REG_A, BPF_REG_CTX, insn);
+ insn += cnt - 1;
break;
case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
@@ -1215,6 +1232,17 @@ static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off,
case offsetof(struct __sk_buff, queue_mapping):
return convert_skb_access(SKF_AD_QUEUE, dst_reg, src_reg, insn);
+
+ case offsetof(struct __sk_buff, protocol):
+ return convert_skb_access(SKF_AD_PROTOCOL, dst_reg, src_reg, insn);
+
+ case offsetof(struct __sk_buff, vlan_present):
+ return convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,
+ dst_reg, src_reg, insn);
+
+ case offsetof(struct __sk_buff, vlan_tci):
+ return convert_skb_access(SKF_AD_VLAN_TAG,
+ dst_reg, src_reg, insn);
}
return insn - insn_buf;
diff --git a/samples/bpf/test_verifier.c b/samples/bpf/test_verifier.c
index df6dbb6576f6..75d561f9fd6a 100644
--- a/samples/bpf/test_verifier.c
+++ b/samples/bpf/test_verifier.c
@@ -658,6 +658,15 @@ static struct bpf_test tests[] = {
BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
offsetof(struct __sk_buff, queue_mapping)),
BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, protocol)),
+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, vlan_present)),
+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, vlan_tci)),
+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
--
1.7.9.5
--
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