From c24973957975403521ca76a776c2dfd12fbe9add Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Mon, 16 Mar 2015 18:06:02 -0700 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- 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, -- 2.20.1