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Add IPv6 support to BPF rate limit #1458

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merged 2 commits into from
Sep 18, 2023
Merged

Add IPv6 support to BPF rate limit #1458

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bada7b0
bpf-rate-limit: remove size limits
kevsecurity Sep 12, 2023
a5cb21f
bpf-rate-limit: support IPv6
kevsecurity Sep 12, 2023
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32 changes: 20 additions & 12 deletions bpf/process/types/basic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1766,16 +1766,16 @@ do_action_signal(int signal)

/* The number of bytes per argument to include in the key
* that we use to check for repeating data.
* 16 is good for IPv4 data. Should increase for IPv6.
* 40 is good for IPv6 data.
*/
#define KEY_BYTES_PER_ARG 16
#define KEY_BYTES_PER_ARG 40

struct ratelimit_key {
__u64 func_id;
__u64 retprobe_id;
__u64 action;
__u64 tid;
char data[MAX_POSSIBLE_ARGS * KEY_BYTES_PER_ARG];
__u8 data[MAX_POSSIBLE_ARGS * KEY_BYTES_PER_ARG];
};

struct ratelimit_value {
Expand All @@ -1789,24 +1789,35 @@ struct {
__type(value, struct ratelimit_value);
} ratelimit_map SEC(".maps");

// The value has extra headroom to allow copying argument data without upsetting the verifier.
// This is not hashed when the key is used in the ratelimit_map.
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(max_entries, 1);
__type(key, __u32);
__type(value, __u8[sizeof(struct ratelimit_key) + 128]);
} ratelimit_heap SEC(".maps");

// This is zeroed memory that we NEVER write to, and use to copy over reusable heap in order
// to zero it.
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(max_entries, 1);
__type(key, __u32);
__type(value, __u8[sizeof(struct ratelimit_key) + 128]);
} ratelimit_ro_heap SEC(".maps");
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would be nice to preface with tg_ratelimit_ro_heap and above so that bpftool reports them with tetragon 'tg' map preface. Not sure we have hit all the maps yet with the naming convention but will be nice going forward.


#ifdef __LARGE_BPF_PROG
static inline __attribute__((always_inline)) bool
rate_limit(__u64 ratelimit_interval, struct msg_generic_kprobe *e)
{
__u64 curr_time = ktime_get_ns();
__u64 *last_repeat_entry;
struct ratelimit_key *key;
void *ro_heap;
__u32 zero = 0;
__u32 index = 0;
__u32 key_index = 0;
__u64 *data64 = 0;
int arg_size;
int i;
__u8 *dst;
Expand All @@ -1817,15 +1828,16 @@ rate_limit(__u64 ratelimit_interval, struct msg_generic_kprobe *e)
key = map_lookup_elem(&ratelimit_heap, &zero);
if (!key)
return false;
ro_heap = map_lookup_elem(&ratelimit_ro_heap, &zero);

key->func_id = e->func_id;
key->retprobe_id = e->retprobe_id;
key->action = e->action;
key->tid = e->tid;

data64 = (__u64 *)key->data;
for (i = 0; i < (MAX_POSSIBLE_ARGS * KEY_BYTES_PER_ARG) / 8; i++)
data64[i] = 0;
// Clean the heap
probe_read(key->data, MAX_POSSIBLE_ARGS * KEY_BYTES_PER_ARG, ro_heap);
dst = key->data;

for (i = 0; i < MAX_POSSIBLE_ARGS; i++) {
if (e->argsoff[i] >= e->common.size)
Expand All @@ -1838,11 +1850,7 @@ rate_limit(__u64 ratelimit_interval, struct msg_generic_kprobe *e)
key_index = e->argsoff[i] & 16383;
if (arg_size > KEY_BYTES_PER_ARG)
arg_size = KEY_BYTES_PER_ARG;
asm volatile("%[dst] = %[data64];\n"
: [dst] "=r"(dst)
: [data64] "r"(data64)
:);
asm volatile("%[arg_size] &= 0x1f;\n"
asm volatile("%[arg_size] &= 0x3f;\n" // ensure this mask is greater than KEY_BYTES_PER_ARG
: [arg_size] "+r"(arg_size)
:);
probe_read(&dst[index], arg_size, &e->args[key_index]);
Expand Down