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.

Alexei Starovoitov committed 11 years ago

Commit c2497391 parent 9cf78673 files · +62 −22Browse files

Unified · Split

3 files

include/uapi/linux/bpf.h +3 −0
net/core/filter.c +50 −22
samples/bpf/test_verifier.c +9 −0

include/uapi/linux/bpf.h+3−0

@@ -178,6 +178,9 @@ struct __sk_buff { · 177 unmodified lines
178	178	__u32 pkt_type;
179	179	__u32 mark;
180	180	__u32 queue_mapping;
	181	+ __u32 protocol;
	182	+ __u32 vlan_present;
	183	+ __u32 vlan_tci;
181	184	};
182	185
183	186	#endif /* _UAPI__LINUX_BPF_H__ */

net/core/filter.c+50−22

@@ -177,6 +177,35 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg, · 176 unmodified lines
177	177	*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
178	178	offsetof(struct sk_buff, queue_mapping));
179	179	break;
	180	+
	181	+ case SKF_AD_PROTOCOL:
	182	+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
	183	+
	184	+ /* dst_reg = (u16 ) (src_reg + offsetof(protocol)) */
	185	+ *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
	186	+ offsetof(struct sk_buff, protocol));
	187	+ /* dst_reg = ntohs(dst_reg) [emitting a nop or swap16] */
	188	+ *insn++ = BPF_ENDIAN(BPF_FROM_BE, dst_reg, 16);
	189	+ break;
	190	+
	191	+ case SKF_AD_VLAN_TAG:
	192	+ case SKF_AD_VLAN_TAG_PRESENT:
	193	+ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
	194	+ BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
	195	+
	196	+ /* dst_reg = (u16 ) (src_reg + offsetof(vlan_tci)) */
	197	+ *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,
	198	+ offsetof(struct sk_buff, vlan_tci));
	199	+ if (skb_field == SKF_AD_VLAN_TAG) {
	200	+ *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg,
	201	+ ~VLAN_TAG_PRESENT);
	202	+ } else {
	203	+ /* dst_reg >>= 12 */
	204	+ *insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 12);
	205	+ /* dst_reg &= 1 */
	206	+ *insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);
	207	+ }
	208	+ break;
180	209	}
181	210
182	211	return insn - insn_buf;
@@ -190,13 +219,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, · 7 unmodified lines
190	219
191	220	switch (fp->k) {
192	221	case SKF_AD_OFF + SKF_AD_PROTOCOL:
193		− BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
194		−
195		− /* A = (u16 ) (CTX + offsetof(protocol)) */
196		− *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
197		− offsetof(struct sk_buff, protocol));
198		− /* A = ntohs(A) [emitting a nop or swap16] */
199		− *insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
	222	+ cnt = convert_skb_access(SKF_AD_PROTOCOL, BPF_REG_A, BPF_REG_CTX, insn);
	223	+ insn += cnt - 1;
200	224	break;
201	225
202	226	case SKF_AD_OFF + SKF_AD_PKTTYPE:
@@ -242,22 +266,15 @@ static bool convert_bpf_extensions(struct sock_filter *fp, · 39 unmodified lines
242	266	break;
243	267
244	268	case SKF_AD_OFF + SKF_AD_VLAN_TAG:
245		− case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
246		− BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
247		− BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
	269	+ cnt = convert_skb_access(SKF_AD_VLAN_TAG,
	270	+ BPF_REG_A, BPF_REG_CTX, insn);
	271	+ insn += cnt - 1;
	272	+ break;
248	273
249		− /* A = (u16 ) (CTX + offsetof(vlan_tci)) */
250		− *insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
251		− offsetof(struct sk_buff, vlan_tci));
252		− if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {
253		− *insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A,
254		− ~VLAN_TAG_PRESENT);
255		− } else {
256		− /* A >>= 12 */
257		− *insn++ = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 12);
258		− /* A &= 1 */
259		− *insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 1);
260		− }
	274	+ case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
	275	+ cnt = convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,
	276	+ BPF_REG_A, BPF_REG_CTX, insn);
	277	+ insn += cnt - 1;
261	278	break;
262	279
263	280	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, · 951 unmodified lines
1215	1232
1216	1233	case offsetof(struct __sk_buff, queue_mapping):
1217	1234	return convert_skb_access(SKF_AD_QUEUE, dst_reg, src_reg, insn);
	1235	+
	1236	+ case offsetof(struct __sk_buff, protocol):
	1237	+ return convert_skb_access(SKF_AD_PROTOCOL, dst_reg, src_reg, insn);
	1238	+
	1239	+ case offsetof(struct __sk_buff, vlan_present):
	1240	+ return convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,
	1241	+ dst_reg, src_reg, insn);
	1242	+
	1243	+ case offsetof(struct __sk_buff, vlan_tci):
	1244	+ return convert_skb_access(SKF_AD_VLAN_TAG,
	1245	+ dst_reg, src_reg, insn);
1218	1246	}
1219	1247
1220	1248	return insn - insn_buf;

samples/bpf/test_verifier.c+9−0

@@ -658,6 +658,15 @@ static struct bpf_test tests[] = { · 657 unmodified lines
658	658	BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
659	659	offsetof(struct __sk_buff, queue_mapping)),
660	660	BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
	661	+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
	662	+ offsetof(struct __sk_buff, protocol)),
	663	+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
	664	+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
	665	+ offsetof(struct __sk_buff, vlan_present)),
	666	+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
	667	+ BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
	668	+ offsetof(struct __sk_buff, vlan_tci)),
	669	+ BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),
661	670	BPF_EXIT_INSN(),
662	671	},
663	672	.result = ACCEPT,

bpf: allow BPF programs access 'protocol' and 'vlan_tci' fields

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