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authorAlexei Starovoitov <ast@plumgrid.com>2015-04-01 17:12:13 -0700
committerDavid S. Miller <davem@davemloft.net>2015-04-06 16:42:35 -0400
commit91bc4822c3d61b9bb7ef66d3b77948a4f9177954 (patch)
treeca92a811b501957c1e876290d305aaf81c8d9aff /samples/bpf
parent5888b93b750609680735d6b8b737703083ef40ff (diff)
downloadlinux-91bc4822c3d61b9bb7ef66d3b77948a4f9177954.tar.gz
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')
-rw-r--r--samples/bpf/Makefile1
-rw-r--r--samples/bpf/bpf_helpers.h7
-rw-r--r--samples/bpf/tcbpf1_kern.c71
3 files changed, 79 insertions, 0 deletions
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 <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";