Skip to content

Commit

Permalink
selftests/bpf: add test for bpf_tcp_gen_syncookie
Browse files Browse the repository at this point in the history 
Modify the existing bpf_tcp_check_syncookie test to also generate a
SYN cookie, pass the packet to the kernel, and verify that the two
cookies are the same (and both valid). Since cloned SKBs are skipped
during generic XDP, this test does not issue a SYN cookie when run in
XDP mode. We therefore only check that a valid SYN cookie was issued at
the TC hook.

Additionally, verify that the MSS for that SYN cookie is within
expected range.

Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
  • Loading branch information
Petar Penkov authored and Alexei Starovoitov committed Jul 31, 2019
1 parent 637f71c commit 91bc357
Show file tree
Hide file tree
Showing 3 changed files with 99 additions and 13 deletions.
48 changes: 43 additions & 5 deletions tools/testing/selftests/bpf/progs/test_tcp_check_syncookie_kern.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,10 +19,29 @@
struct bpf_map_def SEC("maps") results = {
.type = BPF_MAP_TYPE_ARRAY,
.key_size = sizeof(__u32),
.value_size = sizeof(__u64),
.max_entries = 1,
.value_size = sizeof(__u32),
.max_entries = 3,
};

static __always_inline __s64 gen_syncookie(void *data_end, struct bpf_sock *sk,
void *iph, __u32 ip_size,
struct tcphdr *tcph)
{
__u32 thlen = tcph->doff * 4;

if (tcph->syn && !tcph->ack) {
// packet should only have an MSS option
if (thlen != 24)
return 0;

if ((void *)tcph + thlen > data_end)
return 0;

return bpf_tcp_gen_syncookie(sk, iph, ip_size, tcph, thlen);
}
return 0;
}

static __always_inline void check_syncookie(void *ctx, void *data,
void *data_end)
{
Expand All @@ -33,8 +52,10 @@ static __always_inline void check_syncookie(void *ctx, void *data,
struct ipv6hdr *ipv6h;
struct tcphdr *tcph;
int ret;
__u32 key_mss = 2;
__u32 key_gen = 1;
__u32 key = 0;
__u64 value = 1;
__s64 seq_mss;

ethh = data;
if (ethh + 1 > data_end)
Expand Down Expand Up @@ -66,6 +87,9 @@ static __always_inline void check_syncookie(void *ctx, void *data,
if (sk->state != BPF_TCP_LISTEN)
goto release;

seq_mss = gen_syncookie(data_end, sk, ipv4h, sizeof(*ipv4h),
tcph);

ret = bpf_tcp_check_syncookie(sk, ipv4h, sizeof(*ipv4h),
tcph, sizeof(*tcph));
break;
Expand Down Expand Up @@ -95,6 +119,9 @@ static __always_inline void check_syncookie(void *ctx, void *data,
if (sk->state != BPF_TCP_LISTEN)
goto release;

seq_mss = gen_syncookie(data_end, sk, ipv6h, sizeof(*ipv6h),
tcph);

ret = bpf_tcp_check_syncookie(sk, ipv6h, sizeof(*ipv6h),
tcph, sizeof(*tcph));
break;
Expand All @@ -103,8 +130,19 @@ static __always_inline void check_syncookie(void *ctx, void *data,
return;
}

if (ret == 0)
bpf_map_update_elem(&results, &key, &value, 0);
if (seq_mss > 0) {
__u32 cookie = (__u32)seq_mss;
__u32 mss = seq_mss >> 32;

bpf_map_update_elem(&results, &key_gen, &cookie, 0);
bpf_map_update_elem(&results, &key_mss, &mss, 0);
}

if (ret == 0) {
__u32 cookie = bpf_ntohl(tcph->ack_seq) - 1;

bpf_map_update_elem(&results, &key, &cookie, 0);
}

release:
bpf_sk_release(sk);
Expand Down
3 changes: 3 additions & 0 deletions tools/testing/selftests/bpf/test_tcp_check_syncookie.sh
View file
Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,9 @@ setup()
ns1_exec ip link set lo up

ns1_exec sysctl -w net.ipv4.tcp_syncookies=2
ns1_exec sysctl -w net.ipv4.tcp_window_scaling=0
ns1_exec sysctl -w net.ipv4.tcp_timestamps=0
ns1_exec sysctl -w net.ipv4.tcp_sack=0

wait_for_ip 127.0.0.1
wait_for_ip ::1
Expand Down
61 changes: 53 additions & 8 deletions tools/testing/selftests/bpf/test_tcp_check_syncookie_user.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
// Copyright (c) 2018 Facebook
// Copyright (c) 2019 Cloudflare

#include <limits.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
Expand Down Expand Up @@ -77,7 +78,7 @@ static int connect_to_server(int server_fd)
return fd;
}

static int get_map_fd_by_prog_id(int prog_id)
static int get_map_fd_by_prog_id(int prog_id, bool *xdp)
{
struct bpf_prog_info info = {};
__u32 info_len = sizeof(info);
Expand All @@ -104,6 +105,8 @@ static int get_map_fd_by_prog_id(int prog_id)
goto err;
}

*xdp = info.type == BPF_PROG_TYPE_XDP;

map_fd = bpf_map_get_fd_by_id(map_ids[0]);
if (map_fd < 0)
log_err("Failed to get fd by map id %d", map_ids[0]);
Expand All @@ -113,18 +116,32 @@ static int get_map_fd_by_prog_id(int prog_id)
return map_fd;
}

static int run_test(int server_fd, int results_fd)
static int run_test(int server_fd, int results_fd, bool xdp)
{
int client = -1, srv_client = -1;
int ret = 0;
__u32 key = 0;
__u64 value = 0;
__u32 key_gen = 1;
__u32 key_mss = 2;
__u32 value = 0;
__u32 value_gen = 0;
__u32 value_mss = 0;

if (bpf_map_update_elem(results_fd, &key, &value, 0) < 0) {
log_err("Can't clear results");
goto err;
}

if (bpf_map_update_elem(results_fd, &key_gen, &value_gen, 0) < 0) {
log_err("Can't clear results");
goto err;
}

if (bpf_map_update_elem(results_fd, &key_mss, &value_mss, 0) < 0) {
log_err("Can't clear results");
goto err;
}

client = connect_to_server(server_fd);
if (client == -1)
goto err;
Expand All @@ -140,8 +157,35 @@ static int run_test(int server_fd, int results_fd)
goto err;
}

if (value != 1) {
log_err("Didn't match syncookie: %llu", value);
if (value == 0) {
log_err("Didn't match syncookie: %u", value);
goto err;
}

if (bpf_map_lookup_elem(results_fd, &key_gen, &value_gen) < 0) {
log_err("Can't lookup result");
goto err;
}

if (xdp && value_gen == 0) {
// SYN packets do not get passed through generic XDP, skip the
// rest of the test.
printf("Skipping XDP cookie check\n");
goto out;
}

if (bpf_map_lookup_elem(results_fd, &key_mss, &value_mss) < 0) {
log_err("Can't lookup result");
goto err;
}

if (value != value_gen) {
log_err("BPF generated cookie does not match kernel one");
goto err;
}

if (value_mss < 536 || value_mss > USHRT_MAX) {
log_err("Unexpected MSS retrieved");
goto err;
}

Expand All @@ -163,13 +207,14 @@ int main(int argc, char **argv)
int server_v6 = -1;
int results = -1;
int err = 0;
bool xdp;

if (argc < 2) {
fprintf(stderr, "Usage: %s prog_id\n", argv[0]);
exit(1);
}

results = get_map_fd_by_prog_id(atoi(argv[1]));
results = get_map_fd_by_prog_id(atoi(argv[1]), &xdp);
if (results < 0) {
log_err("Can't get map");
goto err;
Expand All @@ -194,10 +239,10 @@ int main(int argc, char **argv)
if (server_v6 == -1)
goto err;

if (run_test(server, results))
if (run_test(server, results, xdp))
goto err;

if (run_test(server_v6, results))
if (run_test(server_v6, results, xdp))
goto err;

printf("ok\n");
Expand Down

0 comments on commit 91bc357

Please sign in to comment.