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linux-stable/samples/bpf/test_lwt_bpf.c
Daniel T. Lee dac808c907 samples/bpf: fix broken lightweight tunnel testing 
The test_lwt_bpf is a script that tests the functionality of BPF through
the output of the ftrace with bpf_trace_printk. Currently, this program
is not operating normally for several reasons.

First of all, this test script can't parse the ftrace results properly.
GNU sed tries to be as greedy as possible when attempting pattern
matching. Due to this, cutting metadata (such as timestamp) from the
log entry of ftrace doesn't work properly, and also desired log isn't
extracted properly. To make sed stripping clearer, 'nocontext-info'
option with the ftrace has been used to remove metadata from the log.
Also, instead of using unclear pattern matching, this commit specifies
an explicit parse pattern.

Also, unlike before when this test was introduced, the way
bpf_trace_printk behaves has changed[1]. The previous bpf_trace_printk
had to always have '\n' in order to print newline, but now that the
bpf_trace_printk call includes newline by default, so '\n' is no longer
needed.

Lastly with the lwt ENCAP_BPF out, the context information with the
sk_buff protocol is preserved. Therefore, this commit changes the
previous test result from 'protocol 0' to 'protocol 8', which means
ETH_P_IP.

[1]: commit ac5a72ea5c ("bpf: Use dedicated bpf_trace_printk event instead of trace_printk()")
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230115071613.125791-4-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-01-15 13:32:45 -08:00

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/* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <stdint.h>
#include <stddef.h>
#include <linux/bpf.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/icmpv6.h>
#include <linux/if_ether.h>
#include <bpf/bpf_helpers.h>
#include <string.h>
# define printk(fmt, ...) \
({ \
char ____fmt[] = fmt; \
bpf_trace_printk(____fmt, sizeof(____fmt), \
##__VA_ARGS__); \
})
#define CB_MAGIC 1234
/* Test: Pass all packets through */
SEC("nop")
int do_nop(struct __sk_buff *skb)
{
return BPF_OK;
}
/* Test: Verify context information can be accessed */
SEC("test_ctx")
int do_test_ctx(struct __sk_buff *skb)
{
skb->cb[0] = CB_MAGIC;
printk("len %d hash %d protocol %d", skb->len, skb->hash,
skb->protocol);
printk("cb %d ingress_ifindex %d ifindex %d", skb->cb[0],
skb->ingress_ifindex, skb->ifindex);
return BPF_OK;
}
/* Test: Ensure skb->cb[] buffer is cleared */
SEC("test_cb")
int do_test_cb(struct __sk_buff *skb)
{
printk("cb0: %x cb1: %x cb2: %x", skb->cb[0], skb->cb[1],
skb->cb[2]);
printk("cb3: %x cb4: %x", skb->cb[3], skb->cb[4]);
return BPF_OK;
}
/* Test: Verify skb data can be read */
SEC("test_data")
int do_test_data(struct __sk_buff *skb)
{
void *data = (void *)(long)skb->data;
void *data_end = (void *)(long)skb->data_end;
struct iphdr *iph = data;
if (data + sizeof(*iph) > data_end) {
printk("packet truncated");
return BPF_DROP;
}
printk("src: %x dst: %x", iph->saddr, iph->daddr);
return BPF_OK;
}
#define IP_CSUM_OFF offsetof(struct iphdr, check)
#define IP_DST_OFF offsetof(struct iphdr, daddr)
#define IP_SRC_OFF offsetof(struct iphdr, saddr)
#define IP_PROTO_OFF offsetof(struct iphdr, protocol)
#define TCP_CSUM_OFF offsetof(struct tcphdr, check)
#define UDP_CSUM_OFF offsetof(struct udphdr, check)
#define IS_PSEUDO 0x10
static inline int rewrite(struct __sk_buff *skb, uint32_t old_ip,
uint32_t new_ip, int rw_daddr)
{
int ret, off = 0, flags = IS_PSEUDO;
uint8_t proto;
ret = bpf_skb_load_bytes(skb, IP_PROTO_OFF, &proto, 1);
if (ret < 0) {
printk("bpf_l4_csum_replace failed: %d", ret);
return BPF_DROP;
}
switch (proto) {
case IPPROTO_TCP:
off = TCP_CSUM_OFF;
break;
case IPPROTO_UDP:
off = UDP_CSUM_OFF;
flags |= BPF_F_MARK_MANGLED_0;
break;
case IPPROTO_ICMPV6:
off = offsetof(struct icmp6hdr, icmp6_cksum);
break;
}
if (off) {
ret = bpf_l4_csum_replace(skb, off, old_ip, new_ip,
flags | sizeof(new_ip));
if (ret < 0) {
printk("bpf_l4_csum_replace failed: %d");
return BPF_DROP;
}
}
ret = bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
if (ret < 0) {
printk("bpf_l3_csum_replace failed: %d", ret);
return BPF_DROP;
}
if (rw_daddr)
ret = bpf_skb_store_bytes(skb, IP_DST_OFF, &new_ip, sizeof(new_ip), 0);
else
ret = bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0);
if (ret < 0) {
printk("bpf_skb_store_bytes() failed: %d", ret);
return BPF_DROP;
}
return BPF_OK;
}
/* Test: Verify skb data can be modified */
SEC("test_rewrite")
int do_test_rewrite(struct __sk_buff *skb)
{
uint32_t old_ip, new_ip = 0x3fea8c0;
int ret;
ret = bpf_skb_load_bytes(skb, IP_DST_OFF, &old_ip, 4);
if (ret < 0) {
printk("bpf_skb_load_bytes failed: %d", ret);
return BPF_DROP;
}
if (old_ip == 0x2fea8c0) {
printk("out: rewriting from %x to %x", old_ip, new_ip);
return rewrite(skb, old_ip, new_ip, 1);
}
return BPF_OK;
}
static inline int __do_push_ll_and_redirect(struct __sk_buff *skb)
{
uint64_t smac = SRC_MAC, dmac = DST_MAC;
int ret, ifindex = DST_IFINDEX;
struct ethhdr ehdr;
ret = bpf_skb_change_head(skb, 14, 0);
if (ret < 0) {
printk("skb_change_head() failed: %d", ret);
}
ehdr.h_proto = __constant_htons(ETH_P_IP);
memcpy(&ehdr.h_source, &smac, 6);
memcpy(&ehdr.h_dest, &dmac, 6);
ret = bpf_skb_store_bytes(skb, 0, &ehdr, sizeof(ehdr), 0);
if (ret < 0) {
printk("skb_store_bytes() failed: %d", ret);
return BPF_DROP;
}
return bpf_redirect(ifindex, 0);
}
SEC("push_ll_and_redirect_silent")
int do_push_ll_and_redirect_silent(struct __sk_buff *skb)
{
return __do_push_ll_and_redirect(skb);
}
SEC("push_ll_and_redirect")
int do_push_ll_and_redirect(struct __sk_buff *skb)
{
int ret, ifindex = DST_IFINDEX;
ret = __do_push_ll_and_redirect(skb);
if (ret >= 0)
printk("redirected to %d", ifindex);
return ret;
}
static inline void __fill_garbage(struct __sk_buff *skb)
{
uint64_t f = 0xFFFFFFFFFFFFFFFF;
bpf_skb_store_bytes(skb, 0, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 8, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 16, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 24, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 32, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 40, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 48, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 56, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 64, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 72, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 80, &f, sizeof(f), 0);
bpf_skb_store_bytes(skb, 88, &f, sizeof(f), 0);
}
SEC("fill_garbage")
int do_fill_garbage(struct __sk_buff *skb)
{
__fill_garbage(skb);
printk("Set initial 96 bytes of header to FF");
return BPF_OK;
}
SEC("fill_garbage_and_redirect")
int do_fill_garbage_and_redirect(struct __sk_buff *skb)
{
int ifindex = DST_IFINDEX;
__fill_garbage(skb);
printk("redirected to %d", ifindex);
return bpf_redirect(ifindex, 0);
}
/* Drop all packets */
SEC("drop_all")
int do_drop_all(struct __sk_buff *skb)
{
printk("dropping with: %d", BPF_DROP);
return BPF_DROP;
}
char _license[] SEC("license") = "GPL";
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