@@ -42,3 +42,4 @@ test_cpp
*.tmp
xdpxceiver
xdp_redirect_multi
+xdp_synproxy
@@ -82,7 +82,7 @@ TEST_PROGS_EXTENDED := with_addr.sh \
TEST_GEN_PROGS_EXTENDED = test_sock_addr test_skb_cgroup_id_user \
flow_dissector_load test_flow_dissector test_tcp_check_syncookie_user \
test_lirc_mode2_user xdping test_cpp runqslower bench bpf_testmod.ko \
- xdpxceiver xdp_redirect_multi
+ xdpxceiver xdp_redirect_multi xdp_synproxy
TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
new file mode 100644
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <network_helpers.h>
+
+#define SYS(cmd) ({ \
+ if (!ASSERT_OK(system(cmd), (cmd))) \
+ goto out; \
+})
+
+#define SYS_OUT(cmd) ({ \
+ FILE *f = popen((cmd), "r"); \
+ if (!ASSERT_OK_PTR(f, (cmd))) \
+ goto out; \
+ f; \
+})
+
+void test_xdp_synproxy(void)
+{
+ int server_fd = -1, client_fd = -1, accept_fd = -1;
+ struct nstoken *ns = NULL;
+ FILE *ctrl_file = NULL;
+ char buf[1024];
+ size_t size;
+
+ SYS("ip netns add synproxy");
+
+ SYS("ip link add tmp0 type veth peer name tmp1");
+ SYS("ip link set tmp1 netns synproxy");
+ SYS("ip link set tmp0 up");
+ SYS("ip addr replace 198.18.0.1/24 dev tmp0");
+
+ // When checksum offload is enabled, the XDP program sees wrong
+ // checksums and drops packets.
+ SYS("ethtool -K tmp0 tx off");
+ // Workaround required for veth.
+ SYS("ip link set tmp0 xdp object xdp_dummy.o section xdp 2> /dev/null");
+
+ ns = open_netns("synproxy");
+ if (!ASSERT_OK_PTR(ns, "setns"))
+ goto out;
+
+ SYS("ip link set lo up");
+ SYS("ip link set tmp1 up");
+ SYS("ip addr replace 198.18.0.2/24 dev tmp1");
+ SYS("sysctl -w net.ipv4.tcp_syncookies=2");
+ SYS("sysctl -w net.ipv4.tcp_timestamps=1");
+ SYS("sysctl -w net.netfilter.nf_conntrack_tcp_loose=0");
+ SYS("iptables -t raw -I PREROUTING \
+ -i tmp1 -p tcp -m tcp --syn --dport 8080 -j CT --notrack");
+ SYS("iptables -t filter -A INPUT \
+ -i tmp1 -p tcp -m tcp --dport 8080 -m state --state INVALID,UNTRACKED \
+ -j SYNPROXY --sack-perm --timestamp --wscale 7 --mss 1460");
+ SYS("iptables -t filter -A INPUT \
+ -i tmp1 -m state --state INVALID -j DROP");
+
+ ctrl_file = SYS_OUT("./xdp_synproxy --iface tmp1 --ports 8080 --single \
+ --mss4 1460 --mss6 1460 --wscale 7 --ttl 64");
+ size = fread(buf, 1, sizeof(buf), ctrl_file);
+ fclose(ctrl_file);
+ if (!ASSERT_OK(memcmp(buf, "Total SYNACKs generated: 0\n", size),
+ "initial SYNACKs"))
+ goto out;
+
+ server_fd = start_server(AF_INET, SOCK_STREAM, "198.18.0.2", 8080, 0);
+ if (!ASSERT_GE(server_fd, 0, "start_server"))
+ goto out;
+
+ close_netns(ns);
+ ns = NULL;
+
+ client_fd = connect_to_fd(server_fd, 10000);
+ if (!ASSERT_GE(client_fd, 0, "connect_to_fd"))
+ goto out;
+
+ accept_fd = accept(server_fd, NULL, NULL);
+ if (!ASSERT_GE(accept_fd, 0, "accept"))
+ goto out;
+
+ ns = open_netns("synproxy");
+ if (!ASSERT_OK_PTR(ns, "setns"))
+ goto out;
+
+ ctrl_file = SYS_OUT("./xdp_synproxy --iface tmp1 --single");
+ size = fread(buf, 1, sizeof(buf), ctrl_file);
+ fclose(ctrl_file);
+ if (!ASSERT_OK(memcmp(buf, "Total SYNACKs generated: 1\n", size),
+ "SYNACKs after connection"))
+ goto out;
+
+out:
+ if (accept_fd >= 0)
+ close(accept_fd);
+ if (client_fd >= 0)
+ close(client_fd);
+ if (server_fd >= 0)
+ close(server_fd);
+ if (ns)
+ close_netns(ns);
+
+ system("ip netns del synproxy");
+}
new file mode 100644
@@ -0,0 +1,750 @@
+// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+/* Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+#include <asm/errno.h>
+
+#define NSEC_PER_SEC 1000000000L
+
+#define ETH_ALEN 6
+#define ETH_P_IP 0x0800
+#define ETH_P_IPV6 0x86DD
+
+#define tcp_flag_word(tp) (((union tcp_word_hdr *)(tp))->words[3])
+
+#define IP_DF 0x4000
+#define IP_MF 0x2000
+#define IP_OFFSET 0x1fff
+
+#define NEXTHDR_TCP 6
+
+#define TCPOPT_NOP 1
+#define TCPOPT_EOL 0
+#define TCPOPT_MSS 2
+#define TCPOPT_WINDOW 3
+#define TCPOPT_SACK_PERM 4
+#define TCPOPT_TIMESTAMP 8
+
+#define TCPOLEN_MSS 4
+#define TCPOLEN_WINDOW 3
+#define TCPOLEN_SACK_PERM 2
+#define TCPOLEN_TIMESTAMP 10
+
+#define TCP_TS_HZ 1000
+#define TS_OPT_WSCALE_MASK 0xf
+#define TS_OPT_SACK (1 << 4)
+#define TS_OPT_ECN (1 << 5)
+#define TSBITS 6
+#define TSMASK (((__u32)1 << TSBITS) - 1)
+#define TCP_MAX_WSCALE 14U
+
+#define IPV4_MAXLEN 60
+#define TCP_MAXLEN 60
+
+#define DEFAULT_MSS4 1460
+#define DEFAULT_MSS6 1440
+#define DEFAULT_WSCALE 7
+#define DEFAULT_TTL 64
+#define MAX_ALLOWED_PORTS 8
+
+#define swap(a, b) \
+ do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+
+#define __get_unaligned_t(type, ptr) ({ \
+ const struct { type x; } __attribute__((__packed__)) *__pptr = (typeof(__pptr))(ptr); \
+ __pptr->x; \
+})
+
+#define get_unaligned(ptr) __get_unaligned_t(typeof(*(ptr)), (ptr))
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __type(key, __u32);
+ __type(value, __u64);
+ __uint(max_entries, 2);
+} values SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __type(key, __u32);
+ __type(value, __u16);
+ __uint(max_entries, MAX_ALLOWED_PORTS);
+} allowed_ports SEC(".maps");
+
+extern struct nf_conn *bpf_xdp_ct_lookup(struct xdp_md *xdp_ctx,
+ struct bpf_sock_tuple *bpf_tuple,
+ __u32 len_tuple,
+ struct bpf_ct_opts *opts,
+ __u32 len_opts) __ksym;
+
+extern void bpf_ct_release(struct nf_conn *ct) __ksym;
+
+static __always_inline void swap_eth_addr(__u8 *a, __u8 *b)
+{
+ __u8 tmp[ETH_ALEN];
+
+ __builtin_memcpy(tmp, a, ETH_ALEN);
+ __builtin_memcpy(a, b, ETH_ALEN);
+ __builtin_memcpy(b, tmp, ETH_ALEN);
+}
+
+static __always_inline __u16 csum_fold(__u32 csum)
+{
+ csum = (csum & 0xffff) + (csum >> 16);
+ csum = (csum & 0xffff) + (csum >> 16);
+ return (__u16)~csum;
+}
+
+static __always_inline __u16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
+ __u32 len, __u8 proto,
+ __u32 csum)
+{
+ __u64 s = csum;
+
+ s += (__u32)saddr;
+ s += (__u32)daddr;
+#if defined(__BIG_ENDIAN__)
+ s += proto + len;
+#elif defined(__LITTLE_ENDIAN__)
+ s += (proto + len) << 8;
+#else
+#error Unknown endian
+#endif
+ s = (s & 0xffffffff) + (s >> 32);
+ s = (s & 0xffffffff) + (s >> 32);
+
+ return csum_fold((__u32)s);
+}
+
+static __always_inline __u16 csum_ipv6_magic(const struct in6_addr *saddr,
+ const struct in6_addr *daddr,
+ __u32 len, __u8 proto, __u32 csum)
+{
+ __u64 sum = csum;
+ int i;
+
+#pragma unroll
+ for (i = 0; i < 4; i++)
+ sum += (__u32)saddr->in6_u.u6_addr32[i];
+
+#pragma unroll
+ for (i = 0; i < 4; i++)
+ sum += (__u32)daddr->in6_u.u6_addr32[i];
+
+ // Don't combine additions to avoid 32-bit overflow.
+ sum += bpf_htonl(len);
+ sum += bpf_htonl(proto);
+
+ sum = (sum & 0xffffffff) + (sum >> 32);
+ sum = (sum & 0xffffffff) + (sum >> 32);
+
+ return csum_fold((__u32)sum);
+}
+
+static __always_inline __u64 tcp_clock_ns(void)
+{
+ return bpf_ktime_get_ns();
+}
+
+static __always_inline __u32 tcp_ns_to_ts(__u64 ns)
+{
+ return ns / (NSEC_PER_SEC / TCP_TS_HZ);
+}
+
+static __always_inline __u32 tcp_time_stamp_raw(void)
+{
+ return tcp_ns_to_ts(tcp_clock_ns());
+}
+
+struct tcpopt_context {
+ __u8 *ptr;
+ __u8 *end;
+ void *data_end;
+ __be32 *tsecr;
+ __u8 wscale;
+ bool option_timestamp;
+ bool option_sack;
+};
+
+static int tscookie_tcpopt_parse(struct tcpopt_context *ctx)
+{
+ __u8 opcode, opsize;
+
+ if (ctx->ptr >= ctx->end)
+ return 1;
+ if (ctx->ptr >= ctx->data_end)
+ return 1;
+
+ opcode = ctx->ptr[0];
+
+ if (opcode == TCPOPT_EOL)
+ return 1;
+ if (opcode == TCPOPT_NOP) {
+ ++ctx->ptr;
+ return 0;
+ }
+
+ if (ctx->ptr + 1 >= ctx->end)
+ return 1;
+ if (ctx->ptr + 1 >= ctx->data_end)
+ return 1;
+ opsize = ctx->ptr[1];
+ if (opsize < 2)
+ return 1;
+
+ if (ctx->ptr + opsize > ctx->end)
+ return 1;
+
+ switch (opcode) {
+ case TCPOPT_WINDOW:
+ if (opsize == TCPOLEN_WINDOW && ctx->ptr + TCPOLEN_WINDOW <= ctx->data_end)
+ ctx->wscale = ctx->ptr[2] < TCP_MAX_WSCALE ? ctx->ptr[2] : TCP_MAX_WSCALE;
+ break;
+ case TCPOPT_TIMESTAMP:
+ if (opsize == TCPOLEN_TIMESTAMP && ctx->ptr + TCPOLEN_TIMESTAMP <= ctx->data_end) {
+ ctx->option_timestamp = true;
+ /* Client's tsval becomes our tsecr. */
+ *ctx->tsecr = get_unaligned((__be32 *)(ctx->ptr + 2));
+ }
+ break;
+ case TCPOPT_SACK_PERM:
+ if (opsize == TCPOLEN_SACK_PERM)
+ ctx->option_sack = true;
+ break;
+ }
+
+ ctx->ptr += opsize;
+
+ return 0;
+}
+
+static int tscookie_tcpopt_parse_batch(__u32 index, void *context)
+{
+ int i;
+
+ for (i = 0; i < 7; i++)
+ if (tscookie_tcpopt_parse(context))
+ return 1;
+ return 0;
+}
+
+static __always_inline bool tscookie_init(struct tcphdr *tcp_header,
+ __u16 tcp_len, __be32 *tsval,
+ __be32 *tsecr, void *data_end)
+{
+ struct tcpopt_context loop_ctx = {
+ .ptr = (__u8 *)(tcp_header + 1),
+ .end = (__u8 *)tcp_header + tcp_len,
+ .data_end = data_end,
+ .tsecr = tsecr,
+ .wscale = TS_OPT_WSCALE_MASK,
+ .option_timestamp = false,
+ .option_sack = false,
+ };
+ u32 cookie;
+
+ bpf_loop(6, tscookie_tcpopt_parse_batch, &loop_ctx, 0);
+
+ if (!loop_ctx.option_timestamp)
+ return false;
+
+ cookie = tcp_time_stamp_raw() & ~TSMASK;
+ cookie |= loop_ctx.wscale & TS_OPT_WSCALE_MASK;
+ if (loop_ctx.option_sack)
+ cookie |= TS_OPT_SACK;
+ if (tcp_header->ece && tcp_header->cwr)
+ cookie |= TS_OPT_ECN;
+ *tsval = bpf_htonl(cookie);
+
+ return true;
+}
+
+static __always_inline void values_get_tcpipopts(__u16 *mss, __u8 *wscale,
+ __u8 *ttl, bool ipv6)
+{
+ __u32 key = 0;
+ __u64 *value;
+
+ value = bpf_map_lookup_elem(&values, &key);
+ if (value && *value != 0) {
+ if (ipv6)
+ *mss = (*value >> 32) & 0xffff;
+ else
+ *mss = *value & 0xffff;
+ *wscale = (*value >> 16) & 0xf;
+ *ttl = (*value >> 24) & 0xff;
+ return;
+ }
+
+ *mss = ipv6 ? DEFAULT_MSS6 : DEFAULT_MSS4;
+ *wscale = DEFAULT_WSCALE;
+ *ttl = DEFAULT_TTL;
+}
+
+static __always_inline void values_inc_synacks(void)
+{
+ __u32 key = 1;
+ __u32 *value;
+
+ value = bpf_map_lookup_elem(&values, &key);
+ if (value)
+ __sync_fetch_and_add(value, 1);
+}
+
+static __always_inline bool check_port_allowed(__u16 port)
+{
+ __u32 i;
+
+ for (i = 0; i < MAX_ALLOWED_PORTS; i++) {
+ __u32 key = i;
+ __u16 *value;
+
+ value = bpf_map_lookup_elem(&allowed_ports, &key);
+
+ if (!value)
+ break;
+ // 0 is a terminator value. Check it first to avoid matching on
+ // a forbidden port == 0 and returning true.
+ if (*value == 0)
+ break;
+
+ if (*value == port)
+ return true;
+ }
+
+ return false;
+}
+
+struct header_pointers {
+ struct ethhdr *eth;
+ struct iphdr *ipv4;
+ struct ipv6hdr *ipv6;
+ struct tcphdr *tcp;
+ __u16 tcp_len;
+};
+
+static __always_inline int tcp_dissect(void *data, void *data_end,
+ struct header_pointers *hdr)
+{
+ hdr->eth = data;
+ if (hdr->eth + 1 > data_end)
+ return XDP_DROP;
+
+ switch (bpf_ntohs(hdr->eth->h_proto)) {
+ case ETH_P_IP:
+ hdr->ipv6 = NULL;
+
+ hdr->ipv4 = (void *)hdr->eth + sizeof(*hdr->eth);
+ if (hdr->ipv4 + 1 > data_end)
+ return XDP_DROP;
+ if (hdr->ipv4->ihl * 4 < sizeof(*hdr->ipv4))
+ return XDP_DROP;
+ if (hdr->ipv4->version != 4)
+ return XDP_DROP;
+
+ if (hdr->ipv4->protocol != IPPROTO_TCP)
+ return XDP_PASS;
+
+ hdr->tcp = (void *)hdr->ipv4 + hdr->ipv4->ihl * 4;
+ break;
+ case ETH_P_IPV6:
+ hdr->ipv4 = NULL;
+
+ hdr->ipv6 = (void *)hdr->eth + sizeof(*hdr->eth);
+ if (hdr->ipv6 + 1 > data_end)
+ return XDP_DROP;
+ if (hdr->ipv6->version != 6)
+ return XDP_DROP;
+
+ // XXX: Extension headers are not supported and could circumvent
+ // XDP SYN flood protection.
+ if (hdr->ipv6->nexthdr != NEXTHDR_TCP)
+ return XDP_PASS;
+
+ hdr->tcp = (void *)hdr->ipv6 + sizeof(*hdr->ipv6);
+ break;
+ default:
+ // XXX: VLANs will circumvent XDP SYN flood protection.
+ return XDP_PASS;
+ }
+
+ if (hdr->tcp + 1 > data_end)
+ return XDP_DROP;
+ hdr->tcp_len = hdr->tcp->doff * 4;
+ if (hdr->tcp_len < sizeof(*hdr->tcp))
+ return XDP_DROP;
+
+ return XDP_TX;
+}
+
+static __always_inline int tcp_lookup(struct xdp_md *ctx, struct header_pointers *hdr)
+{
+ struct bpf_ct_opts ct_lookup_opts = {
+ .netns_id = BPF_F_CURRENT_NETNS,
+ .l4proto = IPPROTO_TCP,
+ };
+ struct bpf_sock_tuple tup = {};
+ struct nf_conn *ct;
+ __u32 tup_size;
+
+ if (hdr->ipv4) {
+ // TCP doesn't normally use fragments, and XDP can't reassemble them.
+ if ((hdr->ipv4->frag_off & bpf_htons(IP_DF | IP_MF | IP_OFFSET)) != bpf_htons(IP_DF))
+ return XDP_DROP;
+
+ tup.ipv4.saddr = hdr->ipv4->saddr;
+ tup.ipv4.daddr = hdr->ipv4->daddr;
+ tup.ipv4.sport = hdr->tcp->source;
+ tup.ipv4.dport = hdr->tcp->dest;
+ tup_size = sizeof(tup.ipv4);
+ } else if (hdr->ipv6) {
+ __builtin_memcpy(tup.ipv6.saddr, &hdr->ipv6->saddr, sizeof(tup.ipv6.saddr));
+ __builtin_memcpy(tup.ipv6.daddr, &hdr->ipv6->daddr, sizeof(tup.ipv6.daddr));
+ tup.ipv6.sport = hdr->tcp->source;
+ tup.ipv6.dport = hdr->tcp->dest;
+ tup_size = sizeof(tup.ipv6);
+ } else {
+ // The verifier can't track that either ipv4 or ipv6 is not NULL.
+ return XDP_ABORTED;
+ }
+ ct = bpf_xdp_ct_lookup(ctx, &tup, tup_size, &ct_lookup_opts, sizeof(ct_lookup_opts));
+ if (ct) {
+ unsigned long status = ct->status;
+
+ bpf_ct_release(ct);
+ if (status & IPS_CONFIRMED_BIT)
+ return XDP_PASS;
+ } else if (ct_lookup_opts.error != -ENOENT) {
+ return XDP_ABORTED;
+ }
+
+ // error == -ENOENT || !(status & IPS_CONFIRMED_BIT)
+ return XDP_TX;
+}
+
+static __always_inline __u8 tcp_mkoptions(__be32 *buf, __be32 *tsopt, __u16 mss,
+ __u8 wscale)
+{
+ __be32 *start = buf;
+
+ *buf++ = bpf_htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | mss);
+
+ if (!tsopt)
+ return buf - start;
+
+ if (tsopt[0] & bpf_htonl(1 << 4))
+ *buf++ = bpf_htonl((TCPOPT_SACK_PERM << 24) |
+ (TCPOLEN_SACK_PERM << 16) |
+ (TCPOPT_TIMESTAMP << 8) |
+ TCPOLEN_TIMESTAMP);
+ else
+ *buf++ = bpf_htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_NOP << 16) |
+ (TCPOPT_TIMESTAMP << 8) |
+ TCPOLEN_TIMESTAMP);
+ *buf++ = tsopt[0];
+ *buf++ = tsopt[1];
+
+ if ((tsopt[0] & bpf_htonl(0xf)) != bpf_htonl(0xf))
+ *buf++ = bpf_htonl((TCPOPT_NOP << 24) |
+ (TCPOPT_WINDOW << 16) |
+ (TCPOLEN_WINDOW << 8) |
+ wscale);
+
+ return buf - start;
+}
+
+static __always_inline void tcp_gen_synack(struct tcphdr *tcp_header,
+ __u32 cookie, __be32 *tsopt,
+ __u16 mss, __u8 wscale)
+{
+ void *tcp_options;
+
+ tcp_flag_word(tcp_header) = TCP_FLAG_SYN | TCP_FLAG_ACK;
+ if (tsopt && (tsopt[0] & bpf_htonl(1 << 5)))
+ tcp_flag_word(tcp_header) |= TCP_FLAG_ECE;
+ tcp_header->doff = 5; // doff is part of tcp_flag_word.
+ swap(tcp_header->source, tcp_header->dest);
+ tcp_header->ack_seq = bpf_htonl(bpf_ntohl(tcp_header->seq) + 1);
+ tcp_header->seq = bpf_htonl(cookie);
+ tcp_header->window = 0;
+ tcp_header->urg_ptr = 0;
+ tcp_header->check = 0; // Rely on hardware checksum offload.
+
+ tcp_options = (void *)(tcp_header + 1);
+ tcp_header->doff += tcp_mkoptions(tcp_options, tsopt, mss, wscale);
+}
+
+static __always_inline void tcpv4_gen_synack(struct header_pointers *hdr,
+ __u32 cookie, __be32 *tsopt)
+{
+ __u8 wscale;
+ __u16 mss;
+ __u8 ttl;
+
+ values_get_tcpipopts(&mss, &wscale, &ttl, false);
+
+ swap_eth_addr(hdr->eth->h_source, hdr->eth->h_dest);
+
+ swap(hdr->ipv4->saddr, hdr->ipv4->daddr);
+ hdr->ipv4->check = 0; // Rely on hardware checksum offload.
+ hdr->ipv4->tos = 0;
+ hdr->ipv4->id = 0;
+ hdr->ipv4->ttl = ttl;
+
+ tcp_gen_synack(hdr->tcp, cookie, tsopt, mss, wscale);
+
+ hdr->tcp_len = hdr->tcp->doff * 4;
+ hdr->ipv4->tot_len = bpf_htons(sizeof(*hdr->ipv4) + hdr->tcp_len);
+}
+
+static __always_inline void tcpv6_gen_synack(struct header_pointers *hdr,
+ __u32 cookie, __be32 *tsopt)
+{
+ __u8 wscale;
+ __u16 mss;
+ __u8 ttl;
+
+ values_get_tcpipopts(&mss, &wscale, &ttl, true);
+
+ swap_eth_addr(hdr->eth->h_source, hdr->eth->h_dest);
+
+ swap(hdr->ipv6->saddr, hdr->ipv6->daddr);
+ *(__be32 *)hdr->ipv6 = bpf_htonl(0x60000000);
+ hdr->ipv6->hop_limit = ttl;
+
+ tcp_gen_synack(hdr->tcp, cookie, tsopt, mss, wscale);
+
+ hdr->tcp_len = hdr->tcp->doff * 4;
+ hdr->ipv6->payload_len = bpf_htons(hdr->tcp_len);
+}
+
+static __always_inline int syncookie_handle_syn(struct header_pointers *hdr,
+ struct xdp_md *ctx,
+ void *data, void *data_end)
+{
+ __u32 old_pkt_size, new_pkt_size;
+ // Unlike clang 10, clang 11 and 12 generate code that doesn't pass the
+ // BPF verifier if tsopt is not volatile. Volatile forces it to store
+ // the pointer value and use it directly, otherwise tcp_mkoptions is
+ // (mis)compiled like this:
+ // if (!tsopt)
+ // return buf - start;
+ // reg = stored_return_value_of_tscookie_init;
+ // if (reg)
+ // tsopt = tsopt_buf;
+ // else
+ // tsopt = NULL;
+ // ...
+ // *buf++ = tsopt[1];
+ // It creates a dead branch where tsopt is assigned NULL, but the
+ // verifier can't prove it's dead and blocks the program.
+ __be32 * volatile tsopt = NULL;
+ __be32 tsopt_buf[2] = {};
+ __u16 ip_len;
+ __u32 cookie;
+ __s64 value;
+
+ // Checksum is not yet verified, but both checksum failure and TCP
+ // header checks return XDP_DROP, so the order doesn't matter.
+ if (hdr->tcp->fin || hdr->tcp->rst)
+ return XDP_DROP;
+
+ // Issue SYN cookies on allowed ports, drop SYN packets on blocked
+ // ports.
+ if (!check_port_allowed(bpf_ntohs(hdr->tcp->dest)))
+ return XDP_DROP;
+
+ if (hdr->ipv4) {
+ // Check the IPv4 and TCP checksums before creating a SYNACK.
+ value = bpf_csum_diff(0, 0, (void *)hdr->ipv4, hdr->ipv4->ihl * 4, 0);
+ if (value < 0)
+ return XDP_ABORTED;
+ if (csum_fold(value) != 0)
+ return XDP_DROP; // Bad IPv4 checksum.
+
+ value = bpf_csum_diff(0, 0, (void *)hdr->tcp, hdr->tcp_len, 0);
+ if (value < 0)
+ return XDP_ABORTED;
+ if (csum_tcpudp_magic(hdr->ipv4->saddr, hdr->ipv4->daddr,
+ hdr->tcp_len, IPPROTO_TCP, value) != 0)
+ return XDP_DROP; // Bad TCP checksum.
+
+ ip_len = sizeof(*hdr->ipv4);
+
+ value = bpf_tcp_raw_gen_syncookie_ipv4(hdr->ipv4, hdr->tcp,
+ hdr->tcp_len);
+ } else if (hdr->ipv6) {
+ // Check the TCP checksum before creating a SYNACK.
+ value = bpf_csum_diff(0, 0, (void *)hdr->tcp, hdr->tcp_len, 0);
+ if (value < 0)
+ return XDP_ABORTED;
+ if (csum_ipv6_magic(&hdr->ipv6->saddr, &hdr->ipv6->daddr,
+ hdr->tcp_len, IPPROTO_TCP, value) != 0)
+ return XDP_DROP; // Bad TCP checksum.
+
+ ip_len = sizeof(*hdr->ipv6);
+
+ value = bpf_tcp_raw_gen_syncookie_ipv6(hdr->ipv6, hdr->tcp,
+ hdr->tcp_len);
+ } else {
+ return XDP_ABORTED;
+ }
+
+ if (value < 0)
+ return XDP_ABORTED;
+ cookie = (__u32)value;
+
+ if (tscookie_init((void *)hdr->tcp, hdr->tcp_len,
+ &tsopt_buf[0], &tsopt_buf[1], data_end))
+ tsopt = tsopt_buf;
+
+ // Check that there is enough space for a SYNACK. It also covers
+ // the check that the destination of the __builtin_memmove below
+ // doesn't overflow.
+ if (data + sizeof(*hdr->eth) + ip_len + TCP_MAXLEN > data_end)
+ return XDP_ABORTED;
+
+ if (hdr->ipv4) {
+ if (hdr->ipv4->ihl * 4 > sizeof(*hdr->ipv4)) {
+ struct tcphdr *new_tcp_header;
+
+ new_tcp_header = data + sizeof(*hdr->eth) + sizeof(*hdr->ipv4);
+ __builtin_memmove(new_tcp_header, hdr->tcp, sizeof(*hdr->tcp));
+ hdr->tcp = new_tcp_header;
+
+ hdr->ipv4->ihl = sizeof(*hdr->ipv4) / 4;
+ }
+
+ tcpv4_gen_synack(hdr, cookie, tsopt);
+ } else if (hdr->ipv6) {
+ tcpv6_gen_synack(hdr, cookie, tsopt);
+ } else {
+ return XDP_ABORTED;
+ }
+
+ // Recalculate checksums.
+ hdr->tcp->check = 0;
+ value = bpf_csum_diff(0, 0, (void *)hdr->tcp, hdr->tcp_len, 0);
+ if (value < 0)
+ return XDP_ABORTED;
+ if (hdr->ipv4) {
+ hdr->tcp->check = csum_tcpudp_magic(hdr->ipv4->saddr,
+ hdr->ipv4->daddr,
+ hdr->tcp_len,
+ IPPROTO_TCP,
+ value);
+
+ hdr->ipv4->check = 0;
+ value = bpf_csum_diff(0, 0, (void *)hdr->ipv4, sizeof(*hdr->ipv4), 0);
+ if (value < 0)
+ return XDP_ABORTED;
+ hdr->ipv4->check = csum_fold(value);
+ } else if (hdr->ipv6) {
+ hdr->tcp->check = csum_ipv6_magic(&hdr->ipv6->saddr,
+ &hdr->ipv6->daddr,
+ hdr->tcp_len,
+ IPPROTO_TCP,
+ value);
+ } else {
+ return XDP_ABORTED;
+ }
+
+ // Set the new packet size.
+ old_pkt_size = data_end - data;
+ new_pkt_size = sizeof(*hdr->eth) + ip_len + hdr->tcp->doff * 4;
+ if (bpf_xdp_adjust_tail(ctx, new_pkt_size - old_pkt_size))
+ return XDP_ABORTED;
+
+ values_inc_synacks();
+
+ return XDP_TX;
+}
+
+static __always_inline int syncookie_handle_ack(struct header_pointers *hdr)
+{
+ int err;
+
+ if (hdr->tcp->rst)
+ return XDP_DROP;
+
+ if (hdr->ipv4)
+ err = bpf_tcp_raw_check_syncookie_ipv4(hdr->ipv4, hdr->tcp);
+ else if (hdr->ipv6)
+ err = bpf_tcp_raw_check_syncookie_ipv6(hdr->ipv6, hdr->tcp);
+ else
+ return XDP_ABORTED;
+ if (err)
+ return XDP_DROP;
+
+ return XDP_PASS;
+}
+
+SEC("xdp/syncookie")
+int syncookie_xdp(struct xdp_md *ctx)
+{
+ void *data_end = (void *)(long)ctx->data_end;
+ void *data = (void *)(long)ctx->data;
+ struct header_pointers hdr;
+ __s64 value;
+ int ret;
+
+ struct bpf_ct_opts ct_lookup_opts = {
+ .netns_id = BPF_F_CURRENT_NETNS,
+ .l4proto = IPPROTO_TCP,
+ };
+
+ ret = tcp_dissect(data, data_end, &hdr);
+ if (ret != XDP_TX)
+ return ret;
+
+ ret = tcp_lookup(ctx, &hdr);
+ if (ret != XDP_TX)
+ return ret;
+
+ // Packet is TCP and doesn't belong to an established connection.
+
+ if ((hdr.tcp->syn ^ hdr.tcp->ack) != 1)
+ return XDP_DROP;
+
+ // Grow the TCP header to TCP_MAXLEN to be able to pass any hdr.tcp_len
+ // to bpf_tcp_raw_gen_syncookie_ipv{4,6} and pass the verifier.
+ if (bpf_xdp_adjust_tail(ctx, TCP_MAXLEN - hdr.tcp_len))
+ return XDP_ABORTED;
+
+ data_end = (void *)(long)ctx->data_end;
+ data = (void *)(long)ctx->data;
+
+ if (hdr.ipv4) {
+ hdr.eth = data;
+ hdr.ipv4 = (void *)hdr.eth + sizeof(*hdr.eth);
+ // IPV4_MAXLEN is needed when calculating checksum.
+ // At least sizeof(struct iphdr) is needed here to access ihl.
+ if ((void *)hdr.ipv4 + IPV4_MAXLEN > data_end)
+ return XDP_ABORTED;
+ hdr.tcp = (void *)hdr.ipv4 + hdr.ipv4->ihl * 4;
+ } else if (hdr.ipv6) {
+ hdr.eth = data;
+ hdr.ipv6 = (void *)hdr.eth + sizeof(*hdr.eth);
+ hdr.tcp = (void *)hdr.ipv6 + sizeof(*hdr.ipv6);
+ } else {
+ return XDP_ABORTED;
+ }
+
+ if ((void *)hdr.tcp + TCP_MAXLEN > data_end)
+ return XDP_ABORTED;
+
+ // We run out of registers, tcp_len gets spilled to the stack, and the
+ // verifier forgets its min and max values checked above in tcp_dissect.
+ hdr.tcp_len = hdr.tcp->doff * 4;
+ if (hdr.tcp_len < sizeof(*hdr.tcp))
+ return XDP_ABORTED;
+
+ return hdr.tcp->syn ? syncookie_handle_syn(&hdr, ctx, data, data_end) :
+ syncookie_handle_ack(&hdr);
+}
+
+char _license[] SEC("license") = "GPL";
new file mode 100644
@@ -0,0 +1,418 @@
+// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+/* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */
+
+#include <stdnoreturn.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <getopt.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+#include <net/if.h>
+#include <linux/if_link.h>
+#include <linux/limits.h>
+
+static unsigned int ifindex;
+static __u32 attached_prog_id;
+
+static void noreturn cleanup(int sig)
+{
+ DECLARE_LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
+ int prog_fd;
+ int err;
+
+ if (attached_prog_id == 0)
+ exit(0);
+
+ prog_fd = bpf_prog_get_fd_by_id(attached_prog_id);
+ if (prog_fd < 0) {
+ fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
+ err = bpf_xdp_attach(ifindex, -1, 0, NULL);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n", strerror(-err));
+ fprintf(stderr, "Failed to detach XDP program\n");
+ exit(1);
+ }
+ } else {
+ opts.old_prog_fd = prog_fd;
+ err = bpf_xdp_attach(ifindex, -1, XDP_FLAGS_REPLACE, &opts);
+ close(prog_fd);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_set_link_xdp_fd_opts: %s\n", strerror(-err));
+ // Not an error if already replaced by someone else.
+ if (err != -EEXIST) {
+ fprintf(stderr, "Failed to detach XDP program\n");
+ exit(1);
+ }
+ }
+ }
+ exit(0);
+}
+
+static noreturn void usage(const char *progname)
+{
+ fprintf(stderr, "Usage: %s [--iface <iface>|--prog <prog_id>] [--mss4 <mss ipv4> --mss6 <mss ipv6> --wscale <wscale> --ttl <ttl>] [--ports <port1>,<port2>,...] [--single]\n",
+ progname);
+ exit(1);
+}
+
+static unsigned long parse_arg_ul(const char *progname, const char *arg, unsigned long limit)
+{
+ unsigned long res;
+ char *endptr;
+
+ errno = 0;
+ res = strtoul(arg, &endptr, 10);
+ if (errno != 0 || *endptr != '\0' || arg[0] == '\0' || res > limit)
+ usage(progname);
+
+ return res;
+}
+
+static void parse_options(int argc, char *argv[], unsigned int *ifindex, __u32 *prog_id,
+ __u64 *tcpipopts, char **ports, bool *single)
+{
+ static struct option long_options[] = {
+ { "help", no_argument, NULL, 'h' },
+ { "iface", required_argument, NULL, 'i' },
+ { "prog", required_argument, NULL, 'x' },
+ { "mss4", required_argument, NULL, 4 },
+ { "mss6", required_argument, NULL, 6 },
+ { "wscale", required_argument, NULL, 'w' },
+ { "ttl", required_argument, NULL, 't' },
+ { "ports", required_argument, NULL, 'p' },
+ { "single", no_argument, NULL, 's' },
+ { NULL, 0, NULL, 0 },
+ };
+ unsigned long mss4, mss6, wscale, ttl;
+ unsigned int tcpipopts_mask = 0;
+
+ if (argc < 2)
+ usage(argv[0]);
+
+ *ifindex = 0;
+ *prog_id = 0;
+ *tcpipopts = 0;
+ *ports = NULL;
+ *single = false;
+
+ while (true) {
+ int opt;
+
+ opt = getopt_long(argc, argv, "", long_options, NULL);
+ if (opt == -1)
+ break;
+
+ switch (opt) {
+ case 'h':
+ usage(argv[0]);
+ break;
+ case 'i':
+ *ifindex = if_nametoindex(optarg);
+ if (*ifindex == 0)
+ usage(argv[0]);
+ break;
+ case 'x':
+ *prog_id = parse_arg_ul(argv[0], optarg, UINT32_MAX);
+ if (*prog_id == 0)
+ usage(argv[0]);
+ break;
+ case 4:
+ mss4 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
+ tcpipopts_mask |= 1 << 0;
+ break;
+ case 6:
+ mss6 = parse_arg_ul(argv[0], optarg, UINT16_MAX);
+ tcpipopts_mask |= 1 << 1;
+ break;
+ case 'w':
+ wscale = parse_arg_ul(argv[0], optarg, 14);
+ tcpipopts_mask |= 1 << 2;
+ break;
+ case 't':
+ ttl = parse_arg_ul(argv[0], optarg, UINT8_MAX);
+ tcpipopts_mask |= 1 << 3;
+ break;
+ case 'p':
+ *ports = optarg;
+ break;
+ case 's':
+ *single = true;
+ break;
+ default:
+ usage(argv[0]);
+ }
+ }
+ if (optind < argc)
+ usage(argv[0]);
+
+ if (tcpipopts_mask == 0xf) {
+ if (mss4 == 0 || mss6 == 0 || wscale == 0 || ttl == 0)
+ usage(argv[0]);
+ *tcpipopts = (mss6 << 32) | (ttl << 24) | (wscale << 16) | mss4;
+ } else if (tcpipopts_mask != 0) {
+ usage(argv[0]);
+ }
+
+ if (*ifindex != 0 && *prog_id != 0)
+ usage(argv[0]);
+ if (*ifindex == 0 && *prog_id == 0)
+ usage(argv[0]);
+}
+
+static int syncookie_attach(const char *argv0, unsigned int ifindex)
+{
+ struct bpf_prog_info info = {};
+ __u32 info_len = sizeof(info);
+ char xdp_filename[PATH_MAX];
+ struct bpf_program *prog;
+ struct bpf_object *obj;
+ int prog_fd;
+ int err;
+
+ snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.o", argv0);
+ obj = bpf_object__open_file(xdp_filename, NULL);
+ err = libbpf_get_error(obj);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
+ return err;
+ }
+
+ err = bpf_object__load(obj);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_object__open_file: %s\n", strerror(-err));
+ return err;
+ }
+
+ prog = bpf_object__find_program_by_name(obj, "syncookie_xdp");
+ if (!prog) {
+ fprintf(stderr, "Error: bpf_object__find_program_by_name: program syncookie_xdp was not found\n");
+ return -ENOENT;
+ }
+
+ prog_fd = bpf_program__fd(prog);
+
+ err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_obj_get_info_by_fd: %s\n", strerror(-err));
+ goto out;
+ }
+ attached_prog_id = info.id;
+ signal(SIGINT, cleanup);
+ signal(SIGTERM, cleanup);
+ err = bpf_xdp_attach(ifindex, prog_fd, XDP_FLAGS_UPDATE_IF_NOEXIST, NULL);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_set_link_xdp_fd: %s\n", strerror(-err));
+ signal(SIGINT, SIG_DFL);
+ signal(SIGTERM, SIG_DFL);
+ attached_prog_id = 0;
+ goto out;
+ }
+ err = 0;
+out:
+ bpf_object__close(obj);
+ return err;
+}
+
+static int syncookie_open_bpf_maps(__u32 prog_id, int *values_map_fd, int *ports_map_fd)
+{
+ struct bpf_prog_info prog_info;
+ __u32 map_ids[8];
+ __u32 info_len;
+ int prog_fd;
+ int err;
+ int i;
+
+ *values_map_fd = -1;
+ *ports_map_fd = -1;
+
+ prog_fd = bpf_prog_get_fd_by_id(prog_id);
+ if (prog_fd < 0) {
+ fprintf(stderr, "Error: bpf_prog_get_fd_by_id: %s\n", strerror(-prog_fd));
+ return prog_fd;
+ }
+
+ prog_info = (struct bpf_prog_info) {
+ .nr_map_ids = 8,
+ .map_ids = (__u64)map_ids,
+ };
+ info_len = sizeof(prog_info);
+
+ err = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &info_len);
+ if (err != 0) {
+ fprintf(stderr, "Error: bpf_obj_get_info_by_fd: %s\n", strerror(-err));
+ goto out;
+ }
+
+ if (prog_info.type != BPF_PROG_TYPE_XDP) {
+ fprintf(stderr, "Error: BPF prog type is not BPF_PROG_TYPE_XDP\n");
+ err = -ENOENT;
+ goto out;
+ }
+ if (prog_info.nr_map_ids < 2) {
+ fprintf(stderr, "Error: Found %u BPF maps, expected at least 2\n",
+ prog_info.nr_map_ids);
+ err = -ENOENT;
+ goto out;
+ }
+
+ for (i = 0; i < prog_info.nr_map_ids; i++) {
+ struct bpf_map_info map_info = {};
+ int map_fd;
+
+ err = bpf_map_get_fd_by_id(map_ids[i]);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_map_get_fd_by_id: %s\n", strerror(-err));
+ goto err_close_map_fds;
+ }
+ map_fd = err;
+
+ info_len = sizeof(map_info);
+ err = bpf_obj_get_info_by_fd(map_fd, &map_info, &info_len);
+ if (err != 0) {
+ fprintf(stderr, "Error: bpf_obj_get_info_by_fd: %s\n", strerror(-err));
+ close(map_fd);
+ goto err_close_map_fds;
+ }
+ if (strcmp(map_info.name, "values") == 0) {
+ *values_map_fd = map_fd;
+ continue;
+ }
+ if (strcmp(map_info.name, "allowed_ports") == 0) {
+ *ports_map_fd = map_fd;
+ continue;
+ }
+ close(map_fd);
+ }
+
+ if (*values_map_fd != -1 && *ports_map_fd != -1) {
+ err = 0;
+ goto out;
+ }
+
+ err = -ENOENT;
+
+err_close_map_fds:
+ if (*values_map_fd != -1)
+ close(*values_map_fd);
+ if (*ports_map_fd != -1)
+ close(*ports_map_fd);
+ *values_map_fd = -1;
+ *ports_map_fd = -1;
+
+out:
+ close(prog_fd);
+ return err;
+}
+
+int main(int argc, char *argv[])
+{
+ int values_map_fd, ports_map_fd;
+ __u64 tcpipopts;
+ bool firstiter;
+ __u64 prevcnt;
+ __u32 prog_id;
+ char *ports;
+ bool single;
+ int err = 0;
+
+ parse_options(argc, argv, &ifindex, &prog_id, &tcpipopts, &ports, &single);
+
+ if (prog_id == 0) {
+ err = bpf_xdp_query_id(ifindex, 0, &prog_id);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_get_link_xdp_id: %s\n", strerror(-err));
+ goto out;
+ }
+ if (prog_id == 0) {
+ err = syncookie_attach(argv[0], ifindex);
+ if (err < 0)
+ goto out;
+ prog_id = attached_prog_id;
+ }
+ }
+
+ err = syncookie_open_bpf_maps(prog_id, &values_map_fd, &ports_map_fd);
+ if (err < 0)
+ goto out;
+
+ if (ports) {
+ __u16 port_last = 0;
+ __u32 port_idx = 0;
+ char *p = ports;
+
+ fprintf(stderr, "Replacing allowed ports\n");
+
+ while (p && *p != '\0') {
+ char *token = strsep(&p, ",");
+ __u16 port;
+
+ port = parse_arg_ul(argv[0], token, UINT16_MAX);
+ err = bpf_map_update_elem(ports_map_fd, &port_idx, &port, BPF_ANY);
+ if (err != 0) {
+ fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
+ fprintf(stderr, "Failed to add port %u (index %u)\n",
+ port, port_idx);
+ goto out_close_maps;
+ }
+ fprintf(stderr, "Added port %u\n", port);
+ port_idx++;
+ }
+ err = bpf_map_update_elem(ports_map_fd, &port_idx, &port_last, BPF_ANY);
+ if (err != 0) {
+ fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
+ fprintf(stderr, "Failed to add the terminator value 0 (index %u)\n",
+ port_idx);
+ goto out_close_maps;
+ }
+ }
+
+ if (tcpipopts) {
+ __u32 key = 0;
+
+ fprintf(stderr, "Replacing TCP/IP options\n");
+
+ err = bpf_map_update_elem(values_map_fd, &key, &tcpipopts, BPF_ANY);
+ if (err != 0) {
+ fprintf(stderr, "Error: bpf_map_update_elem: %s\n", strerror(-err));
+ goto out_close_maps;
+ }
+ }
+
+ if ((ports || tcpipopts) && attached_prog_id == 0 && !single)
+ goto out_close_maps;
+
+ prevcnt = 0;
+ firstiter = true;
+ while (true) {
+ __u32 key = 1;
+ __u64 value;
+
+ err = bpf_map_lookup_elem(values_map_fd, &key, &value);
+ if (err != 0) {
+ fprintf(stderr, "Error: bpf_map_lookup_elem: %s\n", strerror(-err));
+ goto out_close_maps;
+ }
+ if (firstiter) {
+ prevcnt = value;
+ firstiter = false;
+ }
+ if (single) {
+ printf("Total SYNACKs generated: %llu\n", value);
+ break;
+ }
+ printf("SYNACKs generated: %llu (total %llu)\n", value - prevcnt, value);
+ prevcnt = value;
+ sleep(1);
+ }
+
+out_close_maps:
+ close(values_map_fd);
+ close(ports_map_fd);
+out:
+ return err == 0 ? 0 : 1;
+}
This commit adds selftests for the new BPF helpers: bpf_tcp_raw_{gen,check}_syncookie_ipv{4,6}. xdp_synproxy_kern.c is a BPF program that generates SYN cookies on allowed TCP ports and sends SYNACKs to clients, accelerating synproxy iptables module. xdp_synproxy.c is a userspace control application that allows to configure the following options in runtime: list of allowed ports, MSS, window scale, TTL. A selftest is added to prog_tests that leverages the above programs to test the functionality of the new helpers. Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> --- tools/testing/selftests/bpf/.gitignore | 1 + tools/testing/selftests/bpf/Makefile | 2 +- .../selftests/bpf/prog_tests/xdp_synproxy.c | 101 +++ .../selftests/bpf/progs/xdp_synproxy_kern.c | 750 ++++++++++++++++++ tools/testing/selftests/bpf/xdp_synproxy.c | 418 ++++++++++ 5 files changed, 1271 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_synproxy.c create mode 100644 tools/testing/selftests/bpf/progs/xdp_synproxy_kern.c create mode 100644 tools/testing/selftests/bpf/xdp_synproxy.c