From 91bc4822c3d61b9bb7ef66d3b77948a4f9177954 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Wed, 1 Apr 2015 17:12:13 -0700 Subject: 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 Acked-by: Daniel Borkmann Signed-off-by: David S. Miller --- samples/bpf/Makefile | 1 + samples/bpf/bpf_helpers.h | 7 +++++ samples/bpf/tcbpf1_kern.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 79 insertions(+) create mode 100644 samples/bpf/tcbpf1_kern.c (limited to 'samples/bpf') diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile index b5b3600dcdf5..d24f51bca465 100644 --- a/samples/bpf/Makefile +++ b/samples/bpf/Makefile @@ -17,6 +17,7 @@ sockex2-objs := bpf_load.o libbpf.o sockex2_user.o always := $(hostprogs-y) always += sockex1_kern.o always += sockex2_kern.o +always += tcbpf1_kern.o HOSTCFLAGS += -I$(objtree)/usr/include diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h index ca0333146006..72540ec1f003 100644 --- a/samples/bpf/bpf_helpers.h +++ b/samples/bpf/bpf_helpers.h @@ -37,4 +37,11 @@ struct bpf_map_def { unsigned int max_entries; }; +static int (*bpf_skb_store_bytes)(void *ctx, int off, void *from, int len, int flags) = + (void *) BPF_FUNC_skb_store_bytes; +static int (*bpf_l3_csum_replace)(void *ctx, int off, int from, int to, int flags) = + (void *) BPF_FUNC_l3_csum_replace; +static int (*bpf_l4_csum_replace)(void *ctx, int off, int from, int to, int flags) = + (void *) BPF_FUNC_l4_csum_replace; + #endif 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 +#include +#include +#include +#include +#include +#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"; -- cgit v1.2.3