/
kprobe_pwru.c
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/
kprobe_pwru.c
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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2020-2021 Martynas Pumputis */
/* Copyright (C) 2021 Authors of Cilium */
/*
* TODO: ipv6 l4 protocol
* According to https://www.rfc-editor.org/rfc/rfc2460, in ipv6 header, the
* transport layer protocol is represented by the Next Header field. However
* ipv6 supports extension headers and recommends to place the transport layer
* protocol at last. So if we want to parse out the transport layer protocol,
* we have to identify all the extension headers, which is quite troublesome.
* Currently it is assumed that there are no ipv6 extension headers.
*/
/*
* WARNING: `bpf_printk()` has special intention in this program: it is used for
* pcap-filter ebpf injection, please see the comment in the `filter_pcap()`. So
* if you want to add additional `bpf_printk()` for debugging, it is likely to
* break the injection and fail the bpf verifier. In this case, it is
* recommended to use perf_output for debugging.
*/
#include "vmlinux.h"
#include "bpf/bpf_helpers.h"
#include "bpf/bpf_core_read.h"
#include "bpf/bpf_tracing.h"
#define PRINT_SKB_STR_SIZE 2048
#define ETH_P_IP 0x800
#define ETH_P_IPV6 0x86dd
const static bool TRUE = true;
union addr {
u32 v4addr;
struct {
u64 d1;
u64 d2;
} v6addr;
} __attribute__((packed));
struct skb_meta {
u32 netns;
u32 mark;
u32 ifindex;
u32 len;
u32 mtu;
u16 protocol;
u16 pad;
} __attribute__((packed));
struct tuple {
union addr saddr;
union addr daddr;
u16 sport;
u16 dport;
u16 l3_proto;
u8 l4_proto;
u8 pad;
} __attribute__((packed));
u64 print_skb_id = 0;
struct event_t {
u32 pid;
u32 type;
u64 addr;
u64 skb_addr;
u64 ts;
typeof(print_skb_id) print_skb_id;
struct skb_meta meta;
struct tuple tuple;
s64 print_stack_id;
u64 param_second;
u32 cpu_id;
} __attribute__((packed));
#define MAX_QUEUE_ENTRIES 10000
struct {
__uint(type, BPF_MAP_TYPE_QUEUE);
__type(value, struct event_t);
__uint(max_entries, MAX_QUEUE_ENTRIES);
} events SEC(".maps");
#define MAX_TRACK_SIZE 1024
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__type(key, __u64);
__type(value, bool);
__uint(max_entries, MAX_TRACK_SIZE);
} skb_addresses SEC(".maps");
struct config {
u32 netns;
u32 mark;
u8 output_timestamp;
u8 output_meta;
u8 output_tuple;
u8 output_skb;
u8 output_stack;
u8 is_set;
u8 track_skb;
} __attribute__((packed));
static volatile const struct config CFG;
#define cfg (&CFG)
#define MAX_STACK_DEPTH 50
struct {
__uint(type, BPF_MAP_TYPE_STACK_TRACE);
__uint(max_entries, 256);
__uint(key_size, sizeof(u32));
__uint(value_size, MAX_STACK_DEPTH * sizeof(u64));
} print_stack_map SEC(".maps");
#ifdef OUTPUT_SKB
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 256);
__type(key, u32);
__type(value, char[PRINT_SKB_STR_SIZE]);
} print_skb_map SEC(".maps");
#endif
static __always_inline u32
get_netns(struct sk_buff *skb) {
u32 netns = BPF_CORE_READ(skb, dev, nd_net.net, ns.inum);
// if skb->dev is not initialized, try to get ns from sk->__sk_common.skc_net.net->ns.inum
if (netns == 0) {
struct sock *sk = BPF_CORE_READ(skb, sk);
if (sk != NULL) {
netns = BPF_CORE_READ(sk, __sk_common.skc_net.net, ns.inum);
}
}
return netns;
}
static __always_inline bool
filter_meta(struct sk_buff *skb) {
if (cfg->netns && get_netns(skb) != cfg->netns) {
return false;
}
if (cfg->mark && BPF_CORE_READ(skb, mark) != cfg->mark) {
return false;
}
return true;
}
#define addr_empty(addr) \
((addr).v6addr.d1 == 0 && (addr).v6addr.d2 == 0)
#define v6addr_equal(addr, bytes) \
({ \
bool is_equal; \
u64 *u64p = (u64 *) (bytes); \
is_equal = (addr).v6addr.d1 == *u64p && (addr).v6addr.d2 == *(u64p + 1); \
is_equal; \
})
static __always_inline bool
filter_pcap(struct sk_buff *skb) {
BPF_CORE_READ(skb, head);
void *skb_head = BPF_CORE_READ(skb, head);
u16 l3_off = BPF_CORE_READ(skb, network_header);
void *data = skb_head + l3_off;
u16 l4_off = BPF_CORE_READ(skb, transport_header);
u16 len = BPF_CORE_READ(skb, len);
void *data_end = skb_head + l4_off + len;
/*
* The next two lines of code won't be executed; they will be replaced
* by ebpf instructions compiled from pcap-filter expression before
* loading to kernel.
* However they are important placeholders to:
* 1. let us know the registers holding data and data_end, which are
* needed to convert cbpf to ebpf;
* 2. leave r0, r1, r2, r3, r4 available for pcap filter ebpf
* instructions;
* 3. mark the position to inject pcap filter ebpf instructions;
*/
bpf_printk("%d %d", data, data_end);
return data < data_end;
}
static __always_inline bool
filter(struct sk_buff *skb) {
return filter_pcap(skb) && filter_meta(skb);
}
static __always_inline void
set_meta(struct sk_buff *skb, struct skb_meta *meta) {
meta->netns = get_netns(skb);
meta->mark = BPF_CORE_READ(skb, mark);
meta->len = BPF_CORE_READ(skb, len);
meta->protocol = BPF_CORE_READ(skb, protocol);
meta->ifindex = BPF_CORE_READ(skb, dev, ifindex);
meta->mtu = BPF_CORE_READ(skb, dev, mtu);
}
static __always_inline void
set_tuple(struct sk_buff *skb, struct tuple *tpl) {
void *skb_head = BPF_CORE_READ(skb, head);
u16 l3_off = BPF_CORE_READ(skb, network_header);
u16 l4_off = BPF_CORE_READ(skb, transport_header);
struct iphdr *l3_hdr = (struct iphdr *) (skb_head + l3_off);
u8 ip_vsn = BPF_CORE_READ_BITFIELD_PROBED(l3_hdr, version);
if (ip_vsn == 4) {
struct iphdr *ip4 = (struct iphdr *) l3_hdr;
BPF_CORE_READ_INTO(&tpl->saddr, ip4, saddr);
BPF_CORE_READ_INTO(&tpl->daddr, ip4, daddr);
tpl->l4_proto = BPF_CORE_READ(ip4, protocol);
tpl->l3_proto = ETH_P_IP;
} else if (ip_vsn == 6) {
struct ipv6hdr *ip6 = (struct ipv6hdr *) l3_hdr;
BPF_CORE_READ_INTO(&tpl->saddr, ip6, saddr);
BPF_CORE_READ_INTO(&tpl->daddr, ip6, daddr);
tpl->l4_proto = BPF_CORE_READ(ip6, nexthdr); // TODO: ipv6 l4 protocol
tpl->l3_proto = ETH_P_IPV6;
}
if (tpl->l4_proto == IPPROTO_TCP) {
struct tcphdr *tcp = (struct tcphdr *) (skb_head + l4_off);
tpl->sport= BPF_CORE_READ(tcp, source);
tpl->dport= BPF_CORE_READ(tcp, dest);
} else if (tpl->l4_proto == IPPROTO_UDP) {
struct udphdr *udp = (struct udphdr *) (skb_head + l4_off);
tpl->sport= BPF_CORE_READ(udp, source);
tpl->dport= BPF_CORE_READ(udp, dest);
}
}
static __always_inline void
set_skb_btf(struct sk_buff *skb, typeof(print_skb_id) *event_id) {
#ifdef OUTPUT_SKB
static struct btf_ptr p = {};
typeof(print_skb_id) id;
char *str;
p.type_id = bpf_core_type_id_kernel(struct sk_buff);
p.ptr = skb;
id = __sync_fetch_and_add(&print_skb_id, 1) % 256;
str = bpf_map_lookup_elem(&print_skb_map, (u32 *) &id);
if (!str) {
return;
}
if (bpf_snprintf_btf(str, PRINT_SKB_STR_SIZE, &p, sizeof(p), 0) < 0) {
return;
}
*event_id = id;
#endif
}
static __always_inline void
set_output(struct pt_regs *ctx, struct sk_buff *skb, struct event_t *event) {
if (cfg->output_meta) {
set_meta(skb, &event->meta);
}
if (cfg->output_tuple) {
set_tuple(skb, &event->tuple);
}
if (cfg->output_skb) {
set_skb_btf(skb, &event->print_skb_id);
}
if (cfg->output_stack) {
event->print_stack_id = bpf_get_stackid(ctx, &print_stack_map, BPF_F_FAST_STACK_CMP);
}
}
static __noinline int
handle_everything(struct sk_buff *skb, struct pt_regs *ctx, bool has_get_func_ip) {
struct event_t event = {};
bool tracked = false;
u64 skb_addr = (u64) skb;
if (cfg->is_set) {
if (cfg->track_skb && bpf_map_lookup_elem(&skb_addresses, &skb_addr)) {
tracked = true;
goto cont;
}
if (!filter(skb)) {
return 0;
}
cont:
set_output(ctx, skb, &event);
}
if (cfg->track_skb && !tracked) {
bpf_map_update_elem(&skb_addresses, &skb_addr, &TRUE, BPF_ANY);
}
event.skb_addr = (u64) skb;
event.pid = bpf_get_current_pid_tgid();
event.addr = has_get_func_ip ? bpf_get_func_ip(ctx) : PT_REGS_IP(ctx);
event.ts = bpf_ktime_get_ns();
event.cpu_id = bpf_get_smp_processor_id();
event.param_second = PT_REGS_PARM2(ctx);
bpf_map_push_elem(&events, &event, BPF_EXIST);
return 0;
}
#ifdef HAS_KPROBE_MULTI
#define PWRU_KPROBE_TYPE "kprobe.multi"
#define PWRU_HAS_GET_FUNC_IP true
#else
#define PWRU_KPROBE_TYPE "kprobe"
#define PWRU_HAS_GET_FUNC_IP false
#endif /* HAS_KPROBE_MULTI */
#define PWRU_ADD_KPROBE(X) \
SEC(PWRU_KPROBE_TYPE "/skb-" #X) \
int kprobe_skb_##X(struct pt_regs *ctx) { \
struct sk_buff *skb = (struct sk_buff *) PT_REGS_PARM##X(ctx); \
return handle_everything(skb, ctx, PWRU_HAS_GET_FUNC_IP); \
}
PWRU_ADD_KPROBE(1)
PWRU_ADD_KPROBE(2)
PWRU_ADD_KPROBE(3)
PWRU_ADD_KPROBE(4)
PWRU_ADD_KPROBE(5)
#undef PWRU_KPROBE
#undef PWRU_HAS_GET_FUNC_IP
#undef PWRU_KPROBE_TYPE
char __license[] SEC("license") = "GPL";