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@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 50 insertions, 22 deletions

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;