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| author | Alexei Starovoitov <ast@plumgrid.com> | 2015-04-02 03:12:13 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-04-06 23:42:35 +0300 |
| commit | 91bc4822c3d61b9bb7ef66d3b77948a4f9177954 (patch) | |
| tree | ca92a811b501957c1e876290d305aaf81c8d9aff /samples/bpf/tcbpf1_kern.c | |
| parent | 5888b93b750609680735d6b8b737703083ef40ff (diff) | |
| download | linux-91bc4822c3d61b9bb7ef66d3b77948a4f9177954.tar.xz | |
tc: bpf: add checksum helpers
Commit 608cd71a9c7c ("tc: bpf: generalize pedit action") has added the
possibility to mangle packet data to BPF programs in the tc pipeline.
This patch adds two helpers bpf_l3_csum_replace() and bpf_l4_csum_replace()
for fixing up the protocol checksums after the packet mangling.
It also adds 'flags' argument to bpf_skb_store_bytes() helper to avoid
unnecessary checksum recomputations when BPF programs adjusting l3/l4
checksums and documents all three helpers in uapi header.
Moreover, a sample program is added to show how BPF programs can make use
of the mangle and csum helpers.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'samples/bpf/tcbpf1_kern.c')
| -rw-r--r-- | samples/bpf/tcbpf1_kern.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/samples/bpf/tcbpf1_kern.c b/samples/bpf/tcbpf1_kern.c new file mode 100644 index 000000000000..7cf3f42a6e39 --- /dev/null +++ b/samples/bpf/tcbpf1_kern.c @@ -0,0 +1,71 @@ +#include <uapi/linux/bpf.h> +#include <uapi/linux/if_ether.h> +#include <uapi/linux/if_packet.h> +#include <uapi/linux/ip.h> +#include <uapi/linux/in.h> +#include <uapi/linux/tcp.h> +#include "bpf_helpers.h" + +/* compiler workaround */ +#define _htonl __builtin_bswap32 + +static inline void set_dst_mac(struct __sk_buff *skb, char *mac) +{ + bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1); +} + +/* use 1 below for ingress qdisc and 0 for egress */ +#if 0 +#undef ETH_HLEN +#define ETH_HLEN 0 +#endif + +#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check)) +#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos)) + +static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos) +{ + __u8 old_tos = load_byte(skb, TOS_OFF); + + bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2); + bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0); +} + +#define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check)) +#define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr)) + +#define IS_PSEUDO 0x10 + +static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip) +{ + __u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF)); + + bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip)); + bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip)); + bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0); +} + +#define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest)) +static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port) +{ + __u16 old_port = htons(load_half(skb, TCP_DPORT_OFF)); + + bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port)); + bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0); +} + +SEC("classifier") +int bpf_prog1(struct __sk_buff *skb) +{ + __u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)); + long *value; + + if (proto == IPPROTO_TCP) { + set_ip_tos(skb, 8); + set_tcp_ip_src(skb, 0xA010101); + set_tcp_dest_port(skb, 5001); + } + + return 0; +} +char _license[] SEC("license") = "GPL"; |