This commit adds a sample for the new BPF helpers: bpf_ct_lookup_tcp,
bpf_tcp_raw_gen_syncookie and bpf_tcp_raw_check_syncookie.
samples/bpf/syncookie_kern.c is a BPF program that generates SYN cookies
on allowed TCP ports and sends SYNACKs to clients, accelerating synproxy
iptables module.
samples/bpf/syncookie_user.c is a userspace control application that
allows to configure the following options in runtime: list of allowed
ports, MSS, window scale, TTL.
samples/bpf/syncookie_test.sh is a script that demonstrates the setup of
synproxy with XDP acceleration.
Signed-off-by: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
---
samples/bpf/.gitignore | 1 +
samples/bpf/Makefile | 3 +
samples/bpf/syncookie_kern.c | 591 ++++++++++++++++++++++++++++++++++
samples/bpf/syncookie_test.sh | 55 ++++
samples/bpf/syncookie_user.c | 388 ++++++++++++++++++++++
5 files changed, 1038 insertions(+)
create mode 100644 samples/bpf/syncookie_kern.c
create mode 100755 samples/bpf/syncookie_test.sh
create mode 100644 samples/bpf/syncookie_user.c
diff --git a/samples/bpf/.gitignore b/samples/bpf/.gitignore
index 0e7bfdbff80a..6b74e835d323 100644
--- a/samples/bpf/.gitignore
+++ b/samples/bpf/.gitignore
@@ -61,3 +61,4 @@ iperf.*
/vmlinux.h
/bpftool/
/libbpf/
+syncookie
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4c5ad15f8d28..59d90c76bfea 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -53,6 +53,7 @@ tprogs-y += task_fd_query
tprogs-y += xdp_sample_pkts
tprogs-y += ibumad
tprogs-y += hbm
+tprogs-y += syncookie
tprogs-y += xdp_redirect_cpu
tprogs-y += xdp_redirect_map_multi
@@ -118,6 +119,7 @@ task_fd_query-objs := task_fd_query_user.o $(TRACE_HELPERS)
xdp_sample_pkts-objs := xdp_sample_pkts_user.o
ibumad-objs := ibumad_user.o
hbm-objs := hbm.o $(CGROUP_HELPERS)
+syncookie-objs := syncookie_user.o
xdp_redirect_map_multi-objs := xdp_redirect_map_multi_user.o $(XDP_SAMPLE)
xdp_redirect_cpu-objs := xdp_redirect_cpu_user.o $(XDP_SAMPLE)
@@ -181,6 +183,7 @@ always-y += ibumad_kern.o
always-y += hbm_out_kern.o
always-y += hbm_edt_kern.o
always-y += xdpsock_kern.o
+always-y += syncookie_kern.o
ifeq ($(ARCH), arm)
# Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
diff --git a/samples/bpf/syncookie_kern.c b/samples/bpf/syncookie_kern.c
new file mode 100644
index 000000000000..b581ae30b650
--- /dev/null
+++ b/samples/bpf/syncookie_kern.c
@@ -0,0 +1,591 @@
+// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+/* Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved. */
+
+#include <stdbool.h>
+#include <stddef.h>
+
+#include <uapi/linux/errno.h>
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/pkt_cls.h>
+#include <uapi/linux/if_ether.h>
+#include <uapi/linux/in.h>
+#include <uapi/linux/ip.h>
+#include <uapi/linux/ipv6.h>
+#include <uapi/linux/tcp.h>
+#include <uapi/linux/netfilter/nf_conntrack_common.h>
+#include <linux/minmax.h>
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+#define DEFAULT_MSS4 1460
+#define DEFAULT_MSS6 1440
+#define DEFAULT_WSCALE 7
+#define DEFAULT_TTL 64
+#define MAX_ALLOWED_PORTS 8
+
+struct bpf_map_def SEC("maps") values = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(__u32),
+ .value_size = sizeof(__u64),
+ .max_entries = 2,
+};
+
+struct bpf_map_def SEC("maps") allowed_ports = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(__u32),
+ .value_size = sizeof(__u16),
+ .max_entries = MAX_ALLOWED_PORTS,
+};
+
+#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 IPV4_MAXLEN 60
+#define TCP_MAXLEN 60
+
+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->s6_addr32[i];
+
+#pragma unroll
+ for (i = 0; i < 4; i++)
+ sum += (__u32)daddr->s6_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 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 __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_bpf_tcp_raw_gen_tscookie;
+ // if (reg == 0)
+ // 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];
+ void *ip_header;
+ __u16 ip_len;
+ __u32 cookie;
+ __s64 value;
+
+ 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_header = hdr->ipv4;
+ ip_len = sizeof(*hdr->ipv4);
+ } 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_header = hdr->ipv6;
+ ip_len = sizeof(*hdr->ipv6);
+ } else {
+ return XDP_ABORTED;
+ }
+
+ // Issue SYN cookies on allowed ports, drop SYN packets on
+ // blocked ports.
+ if (!check_port_allowed(bpf_ntohs(hdr->tcp->dest)))
+ return XDP_DROP;
+
+ value = bpf_tcp_raw_gen_syncookie(ip_header, ip_len,
+ (void *)hdr->tcp, hdr->tcp_len);
+ if (value < 0)
+ return XDP_ABORTED;
+ cookie = (__u32)value;
+
+ if (bpf_tcp_raw_gen_tscookie((void *)hdr->tcp, hdr->tcp_len,
+ tsopt_buf, sizeof(tsopt_buf)) == 0)
+ 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->ipv4)
+ err = bpf_tcp_raw_check_syncookie(hdr->ipv4, sizeof(*hdr->ipv4),
+ (void *)hdr->tcp, hdr->tcp_len);
+ else if (hdr->ipv6)
+ err = bpf_tcp_raw_check_syncookie(hdr->ipv6, sizeof(*hdr->ipv6),
+ (void *)hdr->tcp, hdr->tcp_len);
+ 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;
+ struct bpf_sock_tuple tup;
+ struct bpf_nf_conn *ct;
+ __u32 tup_size;
+ __s64 value;
+ int ret;
+
+ ret = tcp_dissect(data, data_end, &hdr);
+ if (ret != XDP_TX)
+ return ret;
+
+ 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;
+ }
+
+ value = 0; // Flags.
+ ct = bpf_ct_lookup_tcp(ctx, &tup, tup_size, BPF_F_CURRENT_NETNS, &value);
+ if (ct) {
+ unsigned long status = ct->status;
+
+ bpf_ct_release(ct);
+ if (status & IPS_CONFIRMED_BIT)
+ return XDP_PASS;
+ } else if (value != -ENOENT) {
+ return XDP_ABORTED;
+ }
+
+ // value == -ENOENT || !(status & IPS_CONFIRMED_BIT)
+
+ 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 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);
+}
+
+SEC("xdp/dummy")
+int dummy_xdp(struct xdp_md *ctx)
+{
+ // veth requires XDP programs to be set on both sides.
+ return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/samples/bpf/syncookie_test.sh b/samples/bpf/syncookie_test.sh
new file mode 100755
index 000000000000..923f94a7d6f6
--- /dev/null
+++ b/samples/bpf/syncookie_test.sh
@@ -0,0 +1,55 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+# Copyright (c) 2021, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+
+set -e
+
+PORT=8080
+
+DIR="$(dirname "$0")"
+SERVER_PID=
+MONITOR_PID=
+
+cleanup() {
+ set +e
+ [ -n "$SERVER_PID" ] && kill "$SERVER_PID"
+ [ -n "$MONITOR_PID" ] && kill "$MONITOR_PID"
+ ip link del tmp0
+ ip netns del synproxy
+}
+
+trap cleanup EXIT
+
+ip netns add synproxy
+ip netns exec synproxy ip link set lo up
+ip link add tmp0 type veth peer name tmp1
+sleep 1 # Wait, otherwise the IP address is not applied to tmp0.
+ip link set tmp1 netns synproxy
+ip link set tmp0 up
+ip addr replace 198.18.0.1/24 dev tmp0
+ip netns exec synproxy ip link set tmp1 up
+ip netns exec synproxy ip addr replace 198.18.0.2/24 dev tmp1
+ip netns exec synproxy sysctl -w net.ipv4.tcp_syncookies=2
+ip netns exec synproxy sysctl -w net.ipv4.tcp_timestamps=1
+ip netns exec synproxy sysctl -w net.netfilter.nf_conntrack_tcp_loose=0
+ip netns exec synproxy iptables -t raw -I PREROUTING \
+ -i tmp1 -p tcp -m tcp --syn --dport "$PORT" -j CT --notrack
+ip netns exec synproxy iptables -t filter -A INPUT \
+ -i tmp1 -p tcp -m tcp --dport "$PORT" -m state --state INVALID,UNTRACKED \
+ -j SYNPROXY --sack-perm --timestamp --wscale 7 --mss 1460
+ip netns exec synproxy iptables -t filter -A INPUT \
+ -i tmp1 -m state --state INVALID -j DROP
+# When checksum offload is enabled, the XDP program sees wrong checksums and
+# drops packets.
+ethtool -K tmp0 tx off
+# Workaround required for veth.
+ip link set tmp0 xdp object "$DIR/syncookie_kern.o" section xdp/dummy
+ip netns exec synproxy "$DIR/syncookie" --iface tmp1 --ports "$PORT" \
+ --mss4 1460 --mss6 1440 --wscale 7 --ttl 64 &
+MONITOR_PID="$!"
+ip netns exec synproxy python3 -m http.server "$PORT" &
+SERVER_PID="$!"
+echo "Waiting a few seconds for the server to start..."
+sleep 5
+wget 'http://198.18.0.2:8080/' -O /dev/null -o /dev/null
+sleep 1 # Wait for stats to appear.
diff --git a/samples/bpf/syncookie_user.c b/samples/bpf/syncookie_user.c
new file mode 100644
index 000000000000..dcb074405691
--- /dev/null
+++ b/samples/bpf/syncookie_user.c
@@ -0,0 +1,388 @@
+// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+/* Copyright (c) 2021, 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_set_link_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_set_link_xdp_fd(ifindex, -1, 0);
+ 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_fd = prog_fd;
+ err = bpf_set_link_xdp_fd_opts(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>,...]\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)
+{
+ 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' },
+ { 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 = 0;
+
+ 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;
+ 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_object *obj;
+ int prog_fd;
+ int err;
+
+ snprintf(xdp_filename, sizeof(xdp_filename), "%s_kern.o", argv0);
+ err = bpf_prog_load(xdp_filename, BPF_PROG_TYPE_XDP, &obj, &prog_fd);
+ if (err < 0) {
+ fprintf(stderr, "Error: bpf_prog_load: %s\n", strerror(-err));
+ return err;
+ }
+ 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_set_link_xdp_fd(ifindex, prog_fd, XDP_FLAGS_UPDATE_IF_NOEXIST);
+ 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[3];
+ __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 = 3,
+ .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 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);
+ goto err_close_map_fds;
+ }
+
+ err = 0;
+ goto out;
+
+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;
+ int err = 0;
+
+ parse_options(argc, argv, &ifindex, &prog_id, &tcpipopts, &ports);
+
+ if (prog_id == 0) {
+ err = bpf_get_link_xdp_id(ifindex, &prog_id, 0);
+ 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)
+ 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;
+ }
+ 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;
+}
--
2.30.2
