This commit adds a sample selftest to demonstrate how we can use
bpf_sk_assign_tcp_reqsk() as the backend of SYN Proxy.
The test creates IPv4/IPv6 x TCP connections and transfer messages
over them on lo with BPF tc prog attached.
The tc prog will process SYN and returns SYN+ACK with the following
ISN and TS. In a real use case, this part will be done by other
hosts.
MSB LSB
ISN: | 31 ... 8 | 7 6 | 5 | 4 | 3 2 1 0 |
| Hash_1 | MSS | ECN | SACK | WScale |
TS: | 31 ... 8 | 7 ... 0 |
| Random | Hash_2 |
WScale in SYN is reused in SYN+ACK.
The client returns ACK, and tc prog will recalculate ISN and TS
from ACK and validate SYN Cookie.
If it's valid, the prog calls kfunc to allocate a reqsk for skb and
configure the reqsk based on the argument created from SYN Cookie.
Later, the reqsk will be processed in cookie_v[46]_check() to create
a connection.
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
---
tools/testing/selftests/bpf/bpf_kfuncs.h | 10 +
tools/testing/selftests/bpf/config | 1 +
.../bpf/prog_tests/tcp_custom_syncookie.c | 150 +++++
.../selftests/bpf/progs/bpf_tracing_net.h | 16 +
.../selftests/bpf/progs/test_siphash.h | 64 ++
.../bpf/progs/test_tcp_custom_syncookie.c | 572 ++++++++++++++++++
.../bpf/progs/test_tcp_custom_syncookie.h | 140 +++++
7 files changed, 953 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c
create mode 100644 tools/testing/selftests/bpf/progs/test_siphash.h
create mode 100644 tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c
create mode 100644 tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.h
diff --git a/tools/testing/selftests/bpf/bpf_kfuncs.h b/tools/testing/selftests/bpf/bpf_kfuncs.h
index b4e78c1eb37b..23c24f852f4f 100644
--- a/tools/testing/selftests/bpf/bpf_kfuncs.h
+++ b/tools/testing/selftests/bpf/bpf_kfuncs.h
@@ -51,6 +51,16 @@ extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clo
extern int bpf_sock_addr_set_sun_path(struct bpf_sock_addr_kern *sa_kern,
const __u8 *sun_path, __u32 sun_path__sz) __ksym;
+/* Description
+ * Allocate and configure a reqsk and link it with a listener and skb.
+ * Returns
+ * Error code
+ */
+struct sock;
+struct bpf_tcp_req_attrs;
+extern int bpf_sk_assign_tcp_reqsk(struct __sk_buff *skb, struct sock *sk,
+ struct bpf_tcp_req_attrs *attrs, int attrs__sz) __ksym;
+
void *bpf_cast_to_kern_ctx(void *) __ksym;
void *bpf_rdonly_cast(void *obj, __u32 btf_id) __ksym;
diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index c125c441abc7..01f241ea2c67 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -81,6 +81,7 @@ CONFIG_NF_NAT=y
CONFIG_RC_CORE=y
CONFIG_SECURITY=y
CONFIG_SECURITYFS=y
+CONFIG_SYN_COOKIES=y
CONFIG_TEST_BPF=m
CONFIG_USERFAULTFD=y
CONFIG_VSOCKETS=y
diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c b/tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c
new file mode 100644
index 000000000000..eaf441dc7e79
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tcp_custom_syncookie.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+
+#define _GNU_SOURCE
+#include <sched.h>
+#include <stdlib.h>
+#include <net/if.h>
+
+#include "test_progs.h"
+#include "cgroup_helpers.h"
+#include "network_helpers.h"
+#include "test_tcp_custom_syncookie.skel.h"
+
+static struct test_tcp_custom_syncookie_case {
+ int family, type;
+ char addr[16];
+ char name[10];
+} test_cases[] = {
+ {
+ .name = "IPv4 TCP",
+ .family = AF_INET,
+ .type = SOCK_STREAM,
+ .addr = "127.0.0.1",
+ },
+ {
+ .name = "IPv6 TCP",
+ .family = AF_INET6,
+ .type = SOCK_STREAM,
+ .addr = "::1",
+ },
+};
+
+static int setup_netns(void)
+{
+ if (!ASSERT_OK(unshare(CLONE_NEWNET), "create netns"))
+ return -1;
+
+ if (!ASSERT_OK(system("ip link set dev lo up"), "ip"))
+ goto err;
+
+ if (!ASSERT_OK(write_sysctl("/proc/sys/net/ipv4/tcp_ecn", "1"),
+ "write_sysctl"))
+ goto err;
+
+ return 0;
+err:
+ return -1;
+}
+
+static int setup_tc(struct test_tcp_custom_syncookie *skel)
+{
+ LIBBPF_OPTS(bpf_tc_hook, qdisc_lo, .attach_point = BPF_TC_INGRESS);
+ LIBBPF_OPTS(bpf_tc_opts, tc_attach,
+ .prog_fd = bpf_program__fd(skel->progs.tcp_custom_syncookie));
+
+ qdisc_lo.ifindex = if_nametoindex("lo");
+ if (!ASSERT_OK(bpf_tc_hook_create(&qdisc_lo), "qdisc add dev lo clsact"))
+ goto err;
+
+ if (!ASSERT_OK(bpf_tc_attach(&qdisc_lo, &tc_attach),
+ "filter add dev lo ingress"))
+ goto err;
+
+ return 0;
+err:
+ return -1;
+}
+
+#define msg "Hello World"
+#define msglen 11
+
+static void transfer_message(int sender, int receiver)
+{
+ char buf[msglen];
+ int ret;
+
+ ret = send(sender, msg, msglen, 0);
+ if (!ASSERT_EQ(ret, msglen, "send"))
+ return;
+
+ memset(buf, 0, sizeof(buf));
+
+ ret = recv(receiver, buf, msglen, 0);
+ if (!ASSERT_EQ(ret, msglen, "recv"))
+ return;
+
+ ret = strncmp(buf, msg, msglen);
+ if (!ASSERT_EQ(ret, 0, "strncmp"))
+ return;
+}
+
+static void create_connection(struct test_tcp_custom_syncookie_case *test_case)
+{
+ int server, client, child;
+
+ server = start_server(test_case->family, test_case->type, test_case->addr, 0, 0);
+ if (!ASSERT_NEQ(server, -1, "start_server"))
+ return;
+
+ client = connect_to_fd(server, 0);
+ if (!ASSERT_NEQ(client, -1, "connect_to_fd"))
+ goto close_server;
+
+ child = accept(server, NULL, 0);
+ if (!ASSERT_NEQ(child, -1, "accept"))
+ goto close_client;
+
+ transfer_message(client, child);
+ transfer_message(child, client);
+
+ close(child);
+close_client:
+ close(client);
+close_server:
+ close(server);
+}
+
+void test_tcp_custom_syncookie(void)
+{
+ struct test_tcp_custom_syncookie *skel;
+ int i;
+
+ if (setup_netns())
+ return;
+
+ skel = test_tcp_custom_syncookie__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "open_and_load"))
+ return;
+
+ if (setup_tc(skel))
+ goto destroy_skel;
+
+ for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+ if (!test__start_subtest(test_cases[i].name))
+ continue;
+
+ skel->bss->handled_syn = false;
+ skel->bss->handled_ack = false;
+
+ create_connection(&test_cases[i]);
+
+ ASSERT_EQ(skel->bss->handled_syn, true, "SYN is not handled at tc.");
+ ASSERT_EQ(skel->bss->handled_ack, true, "ACK is not handled at tc");
+ }
+
+destroy_skel:
+ system("tc qdisc del dev lo clsact");
+
+ test_tcp_custom_syncookie__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
index 1bdc680b0e0e..49e525ad9856 100644
--- a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
+++ b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
@@ -51,9 +51,25 @@
#define ICSK_TIME_LOSS_PROBE 5
#define ICSK_TIME_REO_TIMEOUT 6
+#define ETH_ALEN 6
#define ETH_HLEN 14
+#define ETH_P_IP 0x0800
#define ETH_P_IPV6 0x86DD
+#define NEXTHDR_TCP 6
+
+#define TCPOPT_NOP 1
+#define TCPOPT_EOL 0
+#define TCPOPT_MSS 2
+#define TCPOPT_WINDOW 3
+#define TCPOPT_TIMESTAMP 8
+#define TCPOPT_SACK_PERM 4
+
+#define TCPOLEN_MSS 4
+#define TCPOLEN_WINDOW 3
+#define TCPOLEN_TIMESTAMP 10
+#define TCPOLEN_SACK_PERM 2
+
#define CHECKSUM_NONE 0
#define CHECKSUM_PARTIAL 3
diff --git a/tools/testing/selftests/bpf/progs/test_siphash.h b/tools/testing/selftests/bpf/progs/test_siphash.h
new file mode 100644
index 000000000000..5d3a7ec36780
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_siphash.h
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+
+#ifndef _TEST_SIPHASH_H
+#define _TEST_SIPHASH_H
+
+/* include/linux/bitops.h */
+static inline u64 rol64(u64 word, unsigned int shift)
+{
+ return (word << (shift & 63)) | (word >> ((-shift) & 63));
+}
+
+/* include/linux/siphash.h */
+#define SIPHASH_PERMUTATION(a, b, c, d) ( \
+ (a) += (b), (b) = rol64((b), 13), (b) ^= (a), (a) = rol64((a), 32), \
+ (c) += (d), (d) = rol64((d), 16), (d) ^= (c), \
+ (a) += (d), (d) = rol64((d), 21), (d) ^= (a), \
+ (c) += (b), (b) = rol64((b), 17), (b) ^= (c), (c) = rol64((c), 32))
+
+#define SIPHASH_CONST_0 0x736f6d6570736575ULL
+#define SIPHASH_CONST_1 0x646f72616e646f6dULL
+#define SIPHASH_CONST_2 0x6c7967656e657261ULL
+#define SIPHASH_CONST_3 0x7465646279746573ULL
+
+/* lib/siphash.c */
+#define SIPROUND SIPHASH_PERMUTATION(v0, v1, v2, v3)
+
+#define PREAMBLE(len) \
+ u64 v0 = SIPHASH_CONST_0; \
+ u64 v1 = SIPHASH_CONST_1; \
+ u64 v2 = SIPHASH_CONST_2; \
+ u64 v3 = SIPHASH_CONST_3; \
+ u64 b = ((u64)(len)) << 56; \
+ v3 ^= key->key[1]; \
+ v2 ^= key->key[0]; \
+ v1 ^= key->key[1]; \
+ v0 ^= key->key[0];
+
+#define POSTAMBLE \
+ v3 ^= b; \
+ SIPROUND; \
+ SIPROUND; \
+ v0 ^= b; \
+ v2 ^= 0xff; \
+ SIPROUND; \
+ SIPROUND; \
+ SIPROUND; \
+ SIPROUND; \
+ return (v0 ^ v1) ^ (v2 ^ v3);
+
+static inline u64 siphash_2u64(const u64 first, const u64 second, const siphash_key_t *key)
+{
+ PREAMBLE(16)
+ v3 ^= first;
+ SIPROUND;
+ SIPROUND;
+ v0 ^= first;
+ v3 ^= second;
+ SIPROUND;
+ SIPROUND;
+ v0 ^= second;
+ POSTAMBLE
+}
+#endif
diff --git a/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c
new file mode 100644
index 000000000000..a5501b29979a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c
@@ -0,0 +1,572 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+#include "bpf_tracing_net.h"
+#include "bpf_kfuncs.h"
+#include "test_siphash.h"
+#include "test_tcp_custom_syncookie.h"
+
+/* Hash is calculated for each client and split into ISN and TS.
+ *
+ * MSB LSB
+ * ISN: | 31 ... 8 | 7 6 | 5 | 4 | 3 2 1 0 |
+ * | Hash_1 | MSS | ECN | SACK | WScale |
+ *
+ * TS: | 31 ... 8 | 7 ... 0 |
+ * | Random | Hash_2 |
+ */
+#define COOKIE_BITS 8
+#define COOKIE_MASK (((__u32)1 << COOKIE_BITS) - 1)
+
+enum {
+ /* 0xf is invalid thus means that SYN did not have WScale. */
+ BPF_SYNCOOKIE_WSCALE_MASK = (1 << 4) - 1,
+ BPF_SYNCOOKIE_SACK = (1 << 4),
+ BPF_SYNCOOKIE_ECN = (1 << 5),
+};
+
+#define MSS_LOCAL_IPV4 65495
+#define MSS_LOCAL_IPV6 65476
+
+const __u16 msstab4[] = {
+ 536,
+ 1300,
+ 1460,
+ MSS_LOCAL_IPV4,
+};
+
+const __u16 msstab6[] = {
+ 1280 - 60, /* IPV6_MIN_MTU - 60 */
+ 1480 - 60,
+ 9000 - 60,
+ MSS_LOCAL_IPV6,
+};
+
+static siphash_key_t test_key_siphash = {
+ { 0x0706050403020100ULL, 0x0f0e0d0c0b0a0908ULL }
+};
+
+struct tcp_syncookie {
+ struct __sk_buff *skb;
+ void *data_end;
+ struct ethhdr *eth;
+ struct iphdr *ipv4;
+ struct ipv6hdr *ipv6;
+ struct tcphdr *tcp;
+ union {
+ char *ptr;
+ __be32 *ptr32;
+ };
+ struct bpf_tcp_req_attrs attrs;
+ u32 cookie;
+ u64 first;
+};
+
+bool handled_syn, handled_ack;
+
+static int tcp_load_headers(struct tcp_syncookie *ctx)
+{
+ ctx->data_end = (void *)(long)ctx->skb->data_end;
+ ctx->eth = (struct ethhdr *)(long)ctx->skb->data;
+
+ if (ctx->eth + 1 > ctx->data_end)
+ goto err;
+
+ switch (bpf_ntohs(ctx->eth->h_proto)) {
+ case ETH_P_IP:
+ ctx->ipv4 = (struct iphdr *)(ctx->eth + 1);
+
+ if (ctx->ipv4 + 1 > ctx->data_end)
+ goto err;
+
+ if (ctx->ipv4->ihl != sizeof(*ctx->ipv4) / 4)
+ goto err;
+
+ if (ctx->ipv4->version != 4)
+ goto err;
+
+ if (ctx->ipv4->protocol != IPPROTO_TCP)
+ goto err;
+
+ ctx->tcp = (struct tcphdr *)(ctx->ipv4 + 1);
+ break;
+ case ETH_P_IPV6:
+ ctx->ipv6 = (struct ipv6hdr *)(ctx->eth + 1);
+
+ if (ctx->ipv6 + 1 > ctx->data_end)
+ goto err;
+
+ if (ctx->ipv6->version != 6)
+ goto err;
+
+ if (ctx->ipv6->nexthdr != NEXTHDR_TCP)
+ goto err;
+
+ ctx->tcp = (struct tcphdr *)(ctx->ipv6 + 1);
+ break;
+ default:
+ goto err;
+ }
+
+ if (ctx->tcp + 1 > ctx->data_end)
+ goto err;
+
+ return 0;
+err:
+ return -1;
+}
+
+static int tcp_reload_headers(struct tcp_syncookie *ctx)
+{
+ /* Without volatile,
+ * R3 32-bit pointer arithmetic prohibited
+ */
+ volatile u64 data_len = ctx->skb->data_end - ctx->skb->data;
+
+ if (ctx->tcp->doff < sizeof(*ctx->tcp) / 4)
+ goto err;
+
+ /* Needed to calculate csum and parse TCP options. */
+ if (bpf_skb_change_tail(ctx->skb, data_len + 60 - ctx->tcp->doff * 4, 0))
+ goto err;
+
+ ctx->data_end = (void *)(long)ctx->skb->data_end;
+ ctx->eth = (struct ethhdr *)(long)ctx->skb->data;
+ if (ctx->ipv4) {
+ ctx->ipv4 = (struct iphdr *)(ctx->eth + 1);
+ ctx->ipv6 = NULL;
+ ctx->tcp = (struct tcphdr *)(ctx->ipv4 + 1);
+ } else {
+ ctx->ipv4 = NULL;
+ ctx->ipv6 = (struct ipv6hdr *)(ctx->eth + 1);
+ ctx->tcp = (struct tcphdr *)(ctx->ipv6 + 1);
+ }
+
+ if ((void *)ctx->tcp + 60 > ctx->data_end)
+ goto err;
+
+ return 0;
+err:
+ return -1;
+}
+
+static __sum16 tcp_v4_csum(struct tcp_syncookie *ctx, __wsum csum)
+{
+ return csum_tcpudp_magic(ctx->ipv4->saddr, ctx->ipv4->daddr,
+ ctx->tcp->doff * 4, IPPROTO_TCP, csum);
+}
+
+static __sum16 tcp_v6_csum(struct tcp_syncookie *ctx, __wsum csum)
+{
+ return csum_ipv6_magic(&ctx->ipv6->saddr, &ctx->ipv6->daddr,
+ ctx->tcp->doff * 4, IPPROTO_TCP, csum);
+}
+
+static int tcp_validate_header(struct tcp_syncookie *ctx)
+{
+ s64 csum;
+
+ if (tcp_reload_headers(ctx))
+ goto err;
+
+ csum = bpf_csum_diff(0, 0, (void *)ctx->tcp, ctx->tcp->doff * 4, 0);
+ if (csum < 0)
+ goto err;
+
+ if (ctx->ipv4) {
+ /* check tcp_v4_csum(csum) is 0 if not on lo. */
+
+ csum = bpf_csum_diff(0, 0, (void *)ctx->ipv4, ctx->ipv4->ihl * 4, 0);
+ if (csum < 0)
+ goto err;
+
+ if (csum_fold(csum) != 0)
+ goto err;
+ } else if (ctx->ipv6) {
+ /* check tcp_v6_csum(csum) is 0 if not on lo. */
+ }
+
+ return 0;
+err:
+ return -1;
+}
+
+static int tcp_parse_option(__u32 index, struct tcp_syncookie *ctx)
+{
+ char opcode, opsize;
+
+ if (ctx->ptr + 1 > ctx->data_end)
+ goto stop;
+
+ opcode = *ctx->ptr++;
+
+ if (opcode == TCPOPT_EOL)
+ goto stop;
+
+ if (opcode == TCPOPT_NOP)
+ goto next;
+
+ if (ctx->ptr + 1 > ctx->data_end)
+ goto stop;
+
+ opsize = *ctx->ptr++;
+
+ if (opsize < 2)
+ goto stop;
+
+ switch (opcode) {
+ case TCPOPT_MSS:
+ if (opsize == TCPOLEN_MSS && ctx->tcp->syn &&
+ ctx->ptr + (TCPOLEN_MSS - 2) < ctx->data_end)
+ ctx->attrs.mss = get_unaligned_be16(ctx->ptr);
+ break;
+ case TCPOPT_WINDOW:
+ if (opsize == TCPOLEN_WINDOW && ctx->tcp->syn &&
+ ctx->ptr + (TCPOLEN_WINDOW - 2) < ctx->data_end) {
+ ctx->attrs.wscale_ok = 1;
+ ctx->attrs.snd_wscale = *ctx->ptr;
+ }
+ break;
+ case TCPOPT_TIMESTAMP:
+ if (opsize == TCPOLEN_TIMESTAMP &&
+ ctx->ptr + (TCPOLEN_TIMESTAMP - 2) < ctx->data_end) {
+ ctx->attrs.rcv_tsval = get_unaligned_be32(ctx->ptr);
+ ctx->attrs.rcv_tsecr = get_unaligned_be32(ctx->ptr + 4);
+
+ if (ctx->tcp->syn && ctx->attrs.rcv_tsecr)
+ ctx->attrs.tstamp_ok = 0;
+ else
+ ctx->attrs.tstamp_ok = 1;
+ }
+ break;
+ case TCPOPT_SACK_PERM:
+ if (opsize == TCPOLEN_SACK_PERM && ctx->tcp->syn &&
+ ctx->ptr + (TCPOLEN_SACK_PERM - 2) < ctx->data_end)
+ ctx->attrs.sack_ok = 1;
+ break;
+ }
+
+ ctx->ptr += opsize - 2;
+next:
+ return 0;
+stop:
+ return 1;
+}
+
+static void tcp_parse_options(struct tcp_syncookie *ctx)
+{
+ ctx->ptr = (char *)(ctx->tcp + 1);
+
+ bpf_loop(40, tcp_parse_option, ctx, 0);
+}
+
+static int tcp_validate_sysctl(struct tcp_syncookie *ctx)
+{
+ if ((ctx->ipv4 && ctx->attrs.mss != MSS_LOCAL_IPV4) ||
+ (ctx->ipv6 && ctx->attrs.mss != MSS_LOCAL_IPV6))
+ goto err;
+
+ if (!ctx->attrs.wscale_ok || ctx->attrs.snd_wscale != 7)
+ goto err;
+
+ if (!ctx->attrs.tstamp_ok)
+ goto err;
+
+ if (!ctx->attrs.sack_ok)
+ goto err;
+
+ if (!ctx->tcp->ece || !ctx->tcp->cwr)
+ goto err;
+
+ return 0;
+err:
+ return -1;
+}
+
+static void tcp_prepare_cookie(struct tcp_syncookie *ctx)
+{
+ u32 seq = bpf_ntohl(ctx->tcp->seq);
+ u64 first = 0, second;
+ int mssind = 0;
+ u32 hash;
+
+ if (ctx->ipv4) {
+ for (mssind = ARRAY_SIZE(msstab4) - 1; mssind; mssind--)
+ if (ctx->attrs.mss >= msstab4[mssind])
+ break;
+
+ ctx->attrs.mss = msstab4[mssind];
+
+ first = (u64)ctx->ipv4->saddr << 32 | ctx->ipv4->daddr;
+ } else if (ctx->ipv6) {
+ for (mssind = ARRAY_SIZE(msstab6) - 1; mssind; mssind--)
+ if (ctx->attrs.mss >= msstab6[mssind])
+ break;
+
+ ctx->attrs.mss = msstab6[mssind];
+
+ first = (u64)ctx->ipv6->saddr.in6_u.u6_addr8[0] << 32 |
+ ctx->ipv6->daddr.in6_u.u6_addr32[0];
+ }
+
+ second = (u64)seq << 32 | ctx->tcp->source << 16 | ctx->tcp->dest;
+ hash = siphash_2u64(first, second, &test_key_siphash);
+
+ if (ctx->attrs.tstamp_ok) {
+ ctx->attrs.rcv_tsecr = bpf_get_prandom_u32();
+ ctx->attrs.rcv_tsecr &= ~COOKIE_MASK;
+ ctx->attrs.rcv_tsecr |= hash & COOKIE_MASK;
+ }
+
+ hash &= ~COOKIE_MASK;
+ hash |= mssind << 6;
+
+ if (ctx->attrs.wscale_ok)
+ hash |= ctx->attrs.snd_wscale & BPF_SYNCOOKIE_WSCALE_MASK;
+
+ if (ctx->attrs.sack_ok)
+ hash |= BPF_SYNCOOKIE_SACK;
+
+ if (ctx->attrs.tstamp_ok && ctx->tcp->ece && ctx->tcp->cwr)
+ hash |= BPF_SYNCOOKIE_ECN;
+
+ ctx->cookie = hash;
+}
+
+static void tcp_write_options(struct tcp_syncookie *ctx)
+{
+ ctx->ptr32 = (__be32 *)(ctx->tcp + 1);
+
+ *ctx->ptr32++ = bpf_htonl(TCPOPT_MSS << 24 | TCPOLEN_MSS << 16 |
+ ctx->attrs.mss);
+
+ if (ctx->attrs.wscale_ok)
+ *ctx->ptr32++ = bpf_htonl(TCPOPT_NOP << 24 |
+ TCPOPT_WINDOW << 16 |
+ TCPOLEN_WINDOW << 8 |
+ ctx->attrs.snd_wscale);
+
+ if (ctx->attrs.tstamp_ok) {
+ if (ctx->attrs.sack_ok)
+ *ctx->ptr32++ = bpf_htonl(TCPOPT_SACK_PERM << 24 |
+ TCPOLEN_SACK_PERM << 16 |
+ TCPOPT_TIMESTAMP << 8 |
+ TCPOLEN_TIMESTAMP);
+ else
+ *ctx->ptr32++ = bpf_htonl(TCPOPT_NOP << 24 |
+ TCPOPT_NOP << 16 |
+ TCPOPT_TIMESTAMP << 8 |
+ TCPOLEN_TIMESTAMP);
+
+ *ctx->ptr32++ = bpf_htonl(ctx->attrs.rcv_tsecr);
+ *ctx->ptr32++ = bpf_htonl(ctx->attrs.rcv_tsval);
+ } else if (ctx->attrs.sack_ok) {
+ *ctx->ptr32++ = bpf_htonl(TCPOPT_NOP << 24 |
+ TCPOPT_NOP << 16 |
+ TCPOPT_SACK_PERM << 8 |
+ TCPOLEN_SACK_PERM);
+ }
+}
+
+static int tcp_handle_syn(struct tcp_syncookie *ctx)
+{
+ s64 csum;
+
+ if (tcp_validate_header(ctx))
+ goto err;
+
+ tcp_parse_options(ctx);
+
+ if (tcp_validate_sysctl(ctx))
+ goto err;
+
+ tcp_prepare_cookie(ctx);
+ tcp_write_options(ctx);
+
+ swap(ctx->tcp->source, ctx->tcp->dest);
+ ctx->tcp->check = 0;
+ ctx->tcp->ack_seq = bpf_htonl(bpf_ntohl(ctx->tcp->seq) + 1);
+ ctx->tcp->seq = bpf_htonl(ctx->cookie);
+ ctx->tcp->doff = ((long)ctx->ptr32 - (long)ctx->tcp) >> 2;
+ ctx->tcp->ack = 1;
+ if (!ctx->attrs.tstamp_ok || !ctx->tcp->ece || !ctx->tcp->cwr)
+ ctx->tcp->ece = 0;
+ ctx->tcp->cwr = 0;
+
+ csum = bpf_csum_diff(0, 0, (void *)ctx->tcp, ctx->tcp->doff * 4, 0);
+ if (csum < 0)
+ goto err;
+
+ if (ctx->ipv4) {
+ swap(ctx->ipv4->saddr, ctx->ipv4->daddr);
+ ctx->tcp->check = tcp_v4_csum(ctx, csum);
+
+ ctx->ipv4->check = 0;
+ ctx->ipv4->tos = 0;
+ ctx->ipv4->tot_len = bpf_htons((long)ctx->ptr32 - (long)ctx->ipv4);
+ ctx->ipv4->id = 0;
+ ctx->ipv4->ttl = 64;
+
+ csum = bpf_csum_diff(0, 0, (void *)ctx->ipv4, sizeof(*ctx->ipv4), 0);
+ if (csum < 0)
+ goto err;
+
+ ctx->ipv4->check = csum_fold(csum);
+ } else if (ctx->ipv6) {
+ swap(ctx->ipv6->saddr, ctx->ipv6->daddr);
+ ctx->tcp->check = tcp_v6_csum(ctx, csum);
+
+ *(__be32 *)ctx->ipv6 = bpf_htonl(0x60000000);
+ ctx->ipv6->payload_len = bpf_htons((long)ctx->ptr32 - (long)ctx->tcp);
+ ctx->ipv6->hop_limit = 64;
+ }
+
+ swap_array(ctx->eth->h_source, ctx->eth->h_dest);
+
+ if (bpf_skb_change_tail(ctx->skb, (long)ctx->ptr32 - (long)ctx->eth, 0))
+ goto err;
+
+ return bpf_redirect(ctx->skb->ifindex, 0);
+err:
+ return TC_ACT_SHOT;
+}
+
+static int tcp_validate_cookie(struct tcp_syncookie *ctx)
+{
+ u32 cookie = bpf_ntohl(ctx->tcp->ack_seq) - 1;
+ u32 seq = bpf_ntohl(ctx->tcp->seq) - 1;
+ u64 first = 0, second;
+ int mssind;
+ u32 hash;
+
+ if (ctx->ipv4)
+ first = (u64)ctx->ipv4->saddr << 32 | ctx->ipv4->daddr;
+ else if (ctx->ipv6)
+ first = (u64)ctx->ipv6->saddr.in6_u.u6_addr8[0] << 32 |
+ ctx->ipv6->daddr.in6_u.u6_addr32[0];
+
+ second = (u64)seq << 32 | ctx->tcp->source << 16 | ctx->tcp->dest;
+ hash = siphash_2u64(first, second, &test_key_siphash);
+
+ if (ctx->attrs.tstamp_ok)
+ hash -= ctx->attrs.rcv_tsecr & COOKIE_MASK;
+ else
+ hash &= ~COOKIE_MASK;
+
+ hash -= cookie & ~COOKIE_MASK;
+ if (hash)
+ goto err;
+
+ mssind = (cookie & (3 << 6)) >> 6;
+ if (ctx->ipv4) {
+ if (mssind > ARRAY_SIZE(msstab4))
+ goto err;
+
+ ctx->attrs.mss = msstab4[mssind];
+ } else {
+ if (mssind > ARRAY_SIZE(msstab6))
+ goto err;
+
+ ctx->attrs.mss = msstab6[mssind];
+ }
+
+ ctx->attrs.snd_wscale = cookie & BPF_SYNCOOKIE_WSCALE_MASK;
+ ctx->attrs.rcv_wscale = ctx->attrs.snd_wscale;
+ ctx->attrs.wscale_ok = ctx->attrs.snd_wscale == BPF_SYNCOOKIE_WSCALE_MASK;
+ ctx->attrs.sack_ok = cookie & BPF_SYNCOOKIE_SACK;
+ ctx->attrs.ecn_ok = cookie & BPF_SYNCOOKIE_ECN;
+
+ return 0;
+err:
+ return -1;
+}
+
+static int tcp_handle_ack(struct tcp_syncookie *ctx)
+{
+ struct bpf_sock_tuple tuple;
+ struct bpf_sock *skc;
+ int ret = TC_ACT_OK;
+ struct sock *sk;
+ u32 tuple_size;
+
+ if (ctx->ipv4) {
+ tuple.ipv4.saddr = ctx->ipv4->saddr;
+ tuple.ipv4.daddr = ctx->ipv4->daddr;
+ tuple.ipv4.sport = ctx->tcp->source;
+ tuple.ipv4.dport = ctx->tcp->dest;
+ tuple_size = sizeof(tuple.ipv4);
+ } else if (ctx->ipv6) {
+ __builtin_memcpy(tuple.ipv6.saddr, &ctx->ipv6->saddr, sizeof(tuple.ipv6.saddr));
+ __builtin_memcpy(tuple.ipv6.daddr, &ctx->ipv6->daddr, sizeof(tuple.ipv6.daddr));
+ tuple.ipv6.sport = ctx->tcp->source;
+ tuple.ipv6.dport = ctx->tcp->dest;
+ tuple_size = sizeof(tuple.ipv6);
+ } else {
+ goto out;
+ }
+
+ skc = bpf_skc_lookup_tcp(ctx->skb, &tuple, tuple_size, -1, 0);
+ if (!skc)
+ goto out;
+
+ if (skc->state != TCP_LISTEN)
+ goto release;
+
+ sk = (struct sock *)bpf_skc_to_tcp_sock(skc);
+ if (!sk)
+ goto err;
+
+ if (tcp_validate_header(ctx))
+ goto err;
+
+ tcp_parse_options(ctx);
+
+ if (tcp_validate_cookie(ctx))
+ goto err;
+
+ ret = bpf_sk_assign_tcp_reqsk(ctx->skb, sk, &ctx->attrs, sizeof(ctx->attrs));
+ if (ret < 0)
+ goto err;
+
+release:
+ bpf_sk_release(skc);
+out:
+ return ret;
+
+err:
+ ret = TC_ACT_SHOT;
+ goto release;
+}
+
+SEC("tc")
+int tcp_custom_syncookie(struct __sk_buff *skb)
+{
+ struct tcp_syncookie ctx = {
+ .skb = skb,
+ };
+
+ if (tcp_load_headers(&ctx))
+ return TC_ACT_OK;
+
+ if (ctx.tcp->rst)
+ return TC_ACT_OK;
+
+ if (ctx.tcp->syn) {
+ if (ctx.tcp->ack)
+ return TC_ACT_OK;
+
+ handled_syn = true;
+
+ return tcp_handle_syn(&ctx);
+ }
+
+ handled_ack = true;
+
+ return tcp_handle_ack(&ctx);
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.h b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.h
new file mode 100644
index 000000000000..29a6a53cf229
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.h
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+
+#ifndef _TEST_TCP_SYNCOOKIE_H
+#define _TEST_TCP_SYNCOOKIE_H
+
+#define __packed __attribute__((__packed__))
+#define __force
+
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+
+#define swap(a, b) \
+ do { \
+ typeof(a) __tmp = (a); \
+ (a) = (b); \
+ (b) = __tmp; \
+ } while (0)
+
+#define swap_array(a, b) \
+ do { \
+ typeof(a) __tmp[sizeof(a)]; \
+ __builtin_memcpy(__tmp, a, sizeof(a)); \
+ __builtin_memcpy(a, b, sizeof(a)); \
+ __builtin_memcpy(b, __tmp, sizeof(a)); \
+ } while (0)
+
+/* asm-generic/unaligned.h */
+#define __get_unaligned_t(type, ptr) ({ \
+ const struct { type x; } __packed * __pptr = (typeof(__pptr))(ptr); \
+ __pptr->x; \
+})
+
+#define get_unaligned(ptr) __get_unaligned_t(typeof(*(ptr)), (ptr))
+
+static inline u16 get_unaligned_be16(const void *p)
+{
+ return bpf_ntohs(__get_unaligned_t(__be16, p));
+}
+
+static inline u32 get_unaligned_be32(const void *p)
+{
+ return bpf_ntohl(__get_unaligned_t(__be32, p));
+}
+
+/* lib/checksum.c */
+static inline u32 from64to32(u64 x)
+{
+ /* add up 32-bit and 32-bit for 32+c bit */
+ x = (x & 0xffffffff) + (x >> 32);
+ /* add up carry.. */
+ x = (x & 0xffffffff) + (x >> 32);
+ return (u32)x;
+}
+
+static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
+ __u32 len, __u8 proto, __wsum sum)
+{
+ unsigned long long s = (__force u32)sum;
+
+ s += (__force u32)saddr;
+ s += (__force u32)daddr;
+#ifdef __BIG_ENDIAN
+ s += proto + len;
+#else
+ s += (proto + len) << 8;
+#endif
+ return (__force __wsum)from64to32(s);
+}
+
+/* asm-generic/checksum.h */
+static inline __sum16 csum_fold(__wsum csum)
+{
+ u32 sum = (__force u32)csum;
+
+ sum = (sum & 0xffff) + (sum >> 16);
+ sum = (sum & 0xffff) + (sum >> 16);
+ return (__force __sum16)~sum;
+}
+
+static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr, __u32 len,
+ __u8 proto, __wsum sum)
+{
+ return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
+}
+
+/* net/ipv6/ip6_checksum.c */
+static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
+ const struct in6_addr *daddr,
+ __u32 len, __u8 proto, __wsum csum)
+{
+ int carry;
+ __u32 ulen;
+ __u32 uproto;
+ __u32 sum = (__force u32)csum;
+
+ sum += (__force u32)saddr->in6_u.u6_addr32[0];
+ carry = (sum < (__force u32)saddr->in6_u.u6_addr32[0]);
+ sum += carry;
+
+ sum += (__force u32)saddr->in6_u.u6_addr32[1];
+ carry = (sum < (__force u32)saddr->in6_u.u6_addr32[1]);
+ sum += carry;
+
+ sum += (__force u32)saddr->in6_u.u6_addr32[2];
+ carry = (sum < (__force u32)saddr->in6_u.u6_addr32[2]);
+ sum += carry;
+
+ sum += (__force u32)saddr->in6_u.u6_addr32[3];
+ carry = (sum < (__force u32)saddr->in6_u.u6_addr32[3]);
+ sum += carry;
+
+ sum += (__force u32)daddr->in6_u.u6_addr32[0];
+ carry = (sum < (__force u32)daddr->in6_u.u6_addr32[0]);
+ sum += carry;
+
+ sum += (__force u32)daddr->in6_u.u6_addr32[1];
+ carry = (sum < (__force u32)daddr->in6_u.u6_addr32[1]);
+ sum += carry;
+
+ sum += (__force u32)daddr->in6_u.u6_addr32[2];
+ carry = (sum < (__force u32)daddr->in6_u.u6_addr32[2]);
+ sum += carry;
+
+ sum += (__force u32)daddr->in6_u.u6_addr32[3];
+ carry = (sum < (__force u32)daddr->in6_u.u6_addr32[3]);
+ sum += carry;
+
+ ulen = (__force u32)bpf_htonl((__u32)len);
+ sum += ulen;
+ carry = (sum < ulen);
+ sum += carry;
+
+ uproto = (__force u32)bpf_htonl(proto);
+ sum += uproto;
+ carry = (sum < uproto);
+ sum += carry;
+
+ return csum_fold((__force __wsum)sum);
+}
+#endif
--
2.30.2
