bpf: allow programs to write to certain skb fields

[karo-tx-linux.git] / samples / bpf / sockex3_kern.c

diff --git a/samples/bpf/sockex3_kern.c b/samples/bpf/sockex3_kern.c
index 2625b987944fc31dd0da6714d22a9653d3b145cc..41ae2fd21b1365bc51de07ac8475058660cfa271 100644 (file)
--- a/samples/bpf/sockex3_kern.c
+++ b/samples/bpf/sockex3_kern.c
@@ -89,7 +89,6 @@ static inline __u32 ipv6_addr_hash(struct __sk_buff *ctx, __u64 off)
 
 struct globals {
        struct flow_keys flow;
-       __u32 nhoff;
 };
 
 struct bpf_map_def SEC("maps") percpu_map = {
@@ -139,7 +138,7 @@ static void update_stats(struct __sk_buff *skb, struct globals *g)
 static __always_inline void parse_ip_proto(struct __sk_buff *skb,
                                           struct globals *g, __u32 ip_proto)
 {
-       __u32 nhoff = g->nhoff;
+       __u32 nhoff = skb->cb[0];
        int poff;
 
        switch (ip_proto) {
@@ -165,7 +164,7 @@ static __always_inline void parse_ip_proto(struct __sk_buff *skb,
                if (gre_flags & GRE_SEQ)
                        nhoff += 4;
 
-               g->nhoff = nhoff;
+               skb->cb[0] = nhoff;
                parse_eth_proto(skb, gre_proto);
                break;
        }
@@ -195,7 +194,7 @@ PROG(PARSE_IP)(struct __sk_buff *skb)
        if (!g)
                return 0;
 
-       nhoff = g->nhoff;
+       nhoff = skb->cb[0];
 
        if (unlikely(ip_is_fragment(skb, nhoff)))
                return 0;
@@ -210,7 +209,7 @@ PROG(PARSE_IP)(struct __sk_buff *skb)
        verlen = load_byte(skb, nhoff + 0/*offsetof(struct iphdr, ihl)*/);
        nhoff += (verlen & 0xF) << 2;
 
-       g->nhoff = nhoff;
+       skb->cb[0] = nhoff;
        parse_ip_proto(skb, g, ip_proto);
        return 0;
 }
@@ -223,7 +222,7 @@ PROG(PARSE_IPV6)(struct __sk_buff *skb)
        if (!g)
                return 0;
 
-       nhoff = g->nhoff;
+       nhoff = skb->cb[0];
 
        ip_proto = load_byte(skb,
                             nhoff + offsetof(struct ipv6hdr, nexthdr));
@@ -233,25 +232,21 @@ PROG(PARSE_IPV6)(struct __sk_buff *skb)
                                     nhoff + offsetof(struct ipv6hdr, daddr));
        nhoff += sizeof(struct ipv6hdr);
 
-       g->nhoff = nhoff;
+       skb->cb[0] = nhoff;
        parse_ip_proto(skb, g, ip_proto);
        return 0;
 }
 
 PROG(PARSE_VLAN)(struct __sk_buff *skb)
 {
-       struct globals *g = this_cpu_globals();
        __u32 nhoff, proto;
 
-       if (!g)
-               return 0;
-
-       nhoff = g->nhoff;
+       nhoff = skb->cb[0];
 
        proto = load_half(skb, nhoff + offsetof(struct vlan_hdr,
                                                h_vlan_encapsulated_proto));
        nhoff += sizeof(struct vlan_hdr);
-       g->nhoff = nhoff;
+       skb->cb[0] = nhoff;
 
        parse_eth_proto(skb, proto);
 
@@ -260,17 +255,13 @@ PROG(PARSE_VLAN)(struct __sk_buff *skb)
 
 PROG(PARSE_MPLS)(struct __sk_buff *skb)
 {
-       struct globals *g = this_cpu_globals();
        __u32 nhoff, label;
 
-       if (!g)
-               return 0;
-
-       nhoff = g->nhoff;
+       nhoff = skb->cb[0];
 
        label = load_word(skb, nhoff);
        nhoff += sizeof(struct mpls_label);
-       g->nhoff = nhoff;
+       skb->cb[0] = nhoff;
 
        if (label & MPLS_LS_S_MASK) {
                __u8 verlen = load_byte(skb, nhoff);
@@ -288,14 +279,10 @@ PROG(PARSE_MPLS)(struct __sk_buff *skb)
 SEC("socket/0")
 int main_prog(struct __sk_buff *skb)
 {
-       struct globals *g = this_cpu_globals();
        __u32 nhoff = ETH_HLEN;
        __u32 proto = load_half(skb, 12);
 
-       if (!g)
-               return 0;
-
-       g->nhoff = nhoff;
+       skb->cb[0] = nhoff;
        parse_eth_proto(skb, proto);
        return 0;
 }