From d9ff286a0f59fa7843549e49bd240393dd7d8b87 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 23 Jan 2019 09:22:27 -0800
Subject: [PATCH] bpf: allow BPF programs access skb_shared_info->gso_segs
field
This adds the ability to read gso_segs from a BPF program.
v3: Use BPF_REG_AX instead of BPF_REG_TMP for the temporary register,
as suggested by Martin.
v2: refined Eddie Hao patch to address Alexei feedback.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Eddie Hao <eddieh@google.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
include/uapi/linux/bpf.h | 1 +
net/core/filter.c | 21 ++++++++++++
tools/include/uapi/linux/bpf.h | 1 +
tools/testing/selftests/bpf/test_verifier.c | 36 +++++++++++++++++++++
4 files changed, 59 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 91c43884f295f..2940a9854f6d8 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2540,6 +2540,7 @@ struct __sk_buff {
__bpf_md_ptr(struct bpf_flow_keys *, flow_keys);
__u64 tstamp;
__u32 wire_len;
+ __u32 gso_segs;
};
struct bpf_tunnel_key {
diff --git a/net/core/filter.c b/net/core/filter.c
index 2b3b436ef5457..8e587dd1da200 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6700,6 +6700,27 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
target_size));
break;
+ case offsetof(struct __sk_buff, gso_segs):
+ /* si->dst_reg = skb_shinfo(SKB); */
+#ifdef NET_SKBUFF_DATA_USES_OFFSET
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),
+ si->dst_reg, si->src_reg,
+ offsetof(struct sk_buff, head));
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
+ BPF_REG_AX, si->src_reg,
+ offsetof(struct sk_buff, end));
+ *insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX);
+#else
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
+ si->dst_reg, si->src_reg,
+ offsetof(struct sk_buff, end));
+#endif
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct skb_shared_info, gso_segs),
+ si->dst_reg, si->dst_reg,
+ bpf_target_off(struct skb_shared_info,
+ gso_segs, 2,
+ target_size));
+ break;
case offsetof(struct __sk_buff, wire_len):
BUILD_BUG_ON(FIELD_SIZEOF(struct qdisc_skb_cb, pkt_len) != 4);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 91c43884f295f..2940a9854f6d8 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2540,6 +2540,7 @@ struct __sk_buff {
__bpf_md_ptr(struct bpf_flow_keys *, flow_keys);
__u64 tstamp;
__u32 wire_len;
+ __u32 gso_segs;
};
struct bpf_tunnel_key {
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 4f67afeec8d90..e4fef6ca8071b 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -5663,6 +5663,42 @@ static struct bpf_test tests[] = {
.result = ACCEPT,
.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
},
+ {
+ "read gso_segs from CGROUP_SKB",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, gso_segs)),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ },
+ {
+ "write gso_segs from CGROUP_SKB",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
+ offsetof(struct __sk_buff, gso_segs)),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .result = REJECT,
+ .result_unpriv = REJECT,
+ .errstr = "invalid bpf_context access off=164 size=4",
+ .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+ },
+ {
+ "read gso_segs from CLS",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, gso_segs)),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ },
{
"multiple registers share map_lookup_elem result",
.insns = {
--
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