@@ -561,8 +561,8 @@ TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c \
network_helpers.c testing_helpers.c \
btf_helpers.c flow_dissector_load.h \
cap_helpers.c test_loader.c xsk.c disasm.c \
- json_writer.c unpriv_helpers.c
-
+ json_writer.c unpriv_helpers.c \
+ ip_check_defrag_frags.h
TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read $(OUTPUT)/bpf_testmod.ko \
$(OUTPUT)/liburandom_read.so \
$(OUTPUT)/xdp_synproxy \
new file mode 100755
@@ -0,0 +1,90 @@
+#!/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+This script helps generate fragmented UDP packets.
+
+While it is technically possible to dynamically generate
+fragmented packets in C, it is much harder to read and write
+said code. `scapy` is relatively industry standard and really
+easy to read / write.
+
+So we choose to write this script that generates a valid C
+header. Rerun script and commit generated file after any
+modifications.
+"""
+
+import argparse
+import os
+
+from scapy.all import *
+
+
+# These constants must stay in sync with `ip_check_defrag.c`
+VETH1_ADDR = "172.16.1.200"
+VETH0_ADDR6 = "fc00::100"
+VETH1_ADDR6 = "fc00::200"
+CLIENT_PORT = 48878
+SERVER_PORT = 48879
+MAGIC_MESSAGE = "THIS IS THE ORIGINAL MESSAGE, PLEASE REASSEMBLE ME"
+
+
+def print_header(f):
+ f.write("// SPDX-License-Identifier: GPL-2.0\n")
+ f.write("/* DO NOT EDIT -- this file is generated */\n")
+ f.write("\n")
+ f.write("#ifndef _IP_CHECK_DEFRAG_FRAGS_H\n")
+ f.write("#define _IP_CHECK_DEFRAG_FRAGS_H\n")
+ f.write("\n")
+ f.write("#include <stdint.h>\n")
+ f.write("\n")
+
+
+def print_frags(f, frags, v6):
+ for idx, frag in enumerate(frags):
+ # 10 bytes per line to keep width in check
+ chunks = [frag[i : i + 10] for i in range(0, len(frag), 10)]
+ chunks_fmted = [", ".join([str(hex(b)) for b in chunk]) for chunk in chunks]
+ suffix = "6" if v6 else ""
+
+ f.write(f"static uint8_t frag{suffix}_{idx}[] = {{\n")
+ for chunk in chunks_fmted:
+ f.write(f"\t{chunk},\n")
+ f.write(f"}};\n")
+
+
+def print_trailer(f):
+ f.write("\n")
+ f.write("#endif /* _IP_CHECK_DEFRAG_FRAGS_H */\n")
+
+
+def main(f):
+ # srcip of 0 is filled in by IP_HDRINCL
+ sip = "0.0.0.0"
+ sip6 = VETH0_ADDR6
+ dip = VETH1_ADDR
+ dip6 = VETH1_ADDR6
+ sport = CLIENT_PORT
+ dport = SERVER_PORT
+ payload = MAGIC_MESSAGE.encode()
+
+ # Disable UDPv4 checksums to keep code simpler
+ pkt = IP(src=sip,dst=dip) / UDP(sport=sport,dport=dport,chksum=0) / Raw(load=payload)
+ # UDPv6 requires a checksum
+ # Also pin the ipv6 fragment header ID, otherwise it's a random value
+ pkt6 = IPv6(src=sip6,dst=dip6) / IPv6ExtHdrFragment(id=0xBEEF) / UDP(sport=sport,dport=dport) / Raw(load=payload)
+
+ frags = [f.build() for f in pkt.fragment(24)]
+ frags6 = [f.build() for f in fragment6(pkt6, 72)]
+
+ print_header(f)
+ print_frags(f, frags, False)
+ print_frags(f, frags6, True)
+ print_trailer(f)
+
+
+if __name__ == "__main__":
+ dir = os.path.dirname(os.path.realpath(__file__))
+ header = f"{dir}/ip_check_defrag_frags.h"
+ with open(header, "w") as f:
+ main(f)
new file mode 100644
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+/* DO NOT EDIT -- this file is generated */
+
+#ifndef _IP_CHECK_DEFRAG_FRAGS_H
+#define _IP_CHECK_DEFRAG_FRAGS_H
+
+#include <stdint.h>
+
+static uint8_t frag_0[] = {
+ 0x45, 0x0, 0x0, 0x2c, 0x0, 0x1, 0x20, 0x0, 0x40, 0x11,
+ 0xac, 0xe8, 0x0, 0x0, 0x0, 0x0, 0xac, 0x10, 0x1, 0xc8,
+ 0xbe, 0xee, 0xbe, 0xef, 0x0, 0x3a, 0x0, 0x0, 0x54, 0x48,
+ 0x49, 0x53, 0x20, 0x49, 0x53, 0x20, 0x54, 0x48, 0x45, 0x20,
+ 0x4f, 0x52, 0x49, 0x47,
+};
+static uint8_t frag_1[] = {
+ 0x45, 0x0, 0x0, 0x2c, 0x0, 0x1, 0x20, 0x3, 0x40, 0x11,
+ 0xac, 0xe5, 0x0, 0x0, 0x0, 0x0, 0xac, 0x10, 0x1, 0xc8,
+ 0x49, 0x4e, 0x41, 0x4c, 0x20, 0x4d, 0x45, 0x53, 0x53, 0x41,
+ 0x47, 0x45, 0x2c, 0x20, 0x50, 0x4c, 0x45, 0x41, 0x53, 0x45,
+ 0x20, 0x52, 0x45, 0x41,
+};
+static uint8_t frag_2[] = {
+ 0x45, 0x0, 0x0, 0x1e, 0x0, 0x1, 0x0, 0x6, 0x40, 0x11,
+ 0xcc, 0xf0, 0x0, 0x0, 0x0, 0x0, 0xac, 0x10, 0x1, 0xc8,
+ 0x53, 0x53, 0x45, 0x4d, 0x42, 0x4c, 0x45, 0x20, 0x4d, 0x45,
+};
+static uint8_t frag6_0[] = {
+ 0x60, 0x0, 0x0, 0x0, 0x0, 0x20, 0x2c, 0x40, 0xfc, 0x0,
+ 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+ 0x0, 0x0, 0x1, 0x0, 0xfc, 0x0, 0x0, 0x0, 0x0, 0x0,
+ 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x2, 0x0,
+ 0x11, 0x0, 0x0, 0x1, 0x0, 0x0, 0xbe, 0xef, 0xbe, 0xee,
+ 0xbe, 0xef, 0x0, 0x3a, 0xd0, 0xf8, 0x54, 0x48, 0x49, 0x53,
+ 0x20, 0x49, 0x53, 0x20, 0x54, 0x48, 0x45, 0x20, 0x4f, 0x52,
+ 0x49, 0x47,
+};
+static uint8_t frag6_1[] = {
+ 0x60, 0x0, 0x0, 0x0, 0x0, 0x20, 0x2c, 0x40, 0xfc, 0x0,
+ 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+ 0x0, 0x0, 0x1, 0x0, 0xfc, 0x0, 0x0, 0x0, 0x0, 0x0,
+ 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x2, 0x0,
+ 0x11, 0x0, 0x0, 0x19, 0x0, 0x0, 0xbe, 0xef, 0x49, 0x4e,
+ 0x41, 0x4c, 0x20, 0x4d, 0x45, 0x53, 0x53, 0x41, 0x47, 0x45,
+ 0x2c, 0x20, 0x50, 0x4c, 0x45, 0x41, 0x53, 0x45, 0x20, 0x52,
+ 0x45, 0x41,
+};
+static uint8_t frag6_2[] = {
+ 0x60, 0x0, 0x0, 0x0, 0x0, 0x12, 0x2c, 0x40, 0xfc, 0x0,
+ 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
+ 0x0, 0x0, 0x1, 0x0, 0xfc, 0x0, 0x0, 0x0, 0x0, 0x0,
+ 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x2, 0x0,
+ 0x11, 0x0, 0x0, 0x30, 0x0, 0x0, 0xbe, 0xef, 0x53, 0x53,
+ 0x45, 0x4d, 0x42, 0x4c, 0x45, 0x20, 0x4d, 0x45,
+};
+
+#endif /* _IP_CHECK_DEFRAG_FRAGS_H */
new file mode 100644
@@ -0,0 +1,282 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <net/if.h>
+#include <linux/netfilter.h>
+#include <network_helpers.h>
+#include "ip_check_defrag.skel.h"
+#include "ip_check_defrag_frags.h"
+
+/*
+ * This selftest spins up a client and an echo server, each in their own
+ * network namespace. The client will send a fragmented message to the server.
+ * The prog attached to the server will shoot down any fragments. Thus, if
+ * the server is able to correctly echo back the message to the client, we will
+ * have verified that netfilter is reassembling packets for us.
+ *
+ * Topology:
+ * =========
+ * NS0 | NS1
+ * |
+ * client | server
+ * ---------- | ----------
+ * | veth0 | --------- | veth1 |
+ * ---------- peer ----------
+ * |
+ * | with bpf
+ */
+
+#define NS0 "defrag_ns0"
+#define NS1 "defrag_ns1"
+#define VETH0 "veth0"
+#define VETH1 "veth1"
+#define VETH0_ADDR "172.16.1.100"
+#define VETH0_ADDR6 "fc00::100"
+/* The following constants must stay in sync with `generate_udp_fragments.py` */
+#define VETH1_ADDR "172.16.1.200"
+#define VETH1_ADDR6 "fc00::200"
+#define CLIENT_PORT 48878
+#define SERVER_PORT 48879
+#define MAGIC_MESSAGE "THIS IS THE ORIGINAL MESSAGE, PLEASE REASSEMBLE ME"
+
+static int setup_topology(bool ipv6)
+{
+ bool up;
+ int i;
+
+ SYS(fail, "ip netns add " NS0);
+ SYS(fail, "ip netns add " NS1);
+ SYS(fail, "ip link add " VETH0 " netns " NS0 " type veth peer name " VETH1 " netns " NS1);
+ if (ipv6) {
+ SYS(fail, "ip -6 -net " NS0 " addr add " VETH0_ADDR6 "/64 dev " VETH0 " nodad");
+ SYS(fail, "ip -6 -net " NS1 " addr add " VETH1_ADDR6 "/64 dev " VETH1 " nodad");
+ } else {
+ SYS(fail, "ip -net " NS0 " addr add " VETH0_ADDR "/24 dev " VETH0);
+ SYS(fail, "ip -net " NS1 " addr add " VETH1_ADDR "/24 dev " VETH1);
+ }
+ SYS(fail, "ip -net " NS0 " link set dev " VETH0 " up");
+ SYS(fail, "ip -net " NS1 " link set dev " VETH1 " up");
+
+ /* Wait for up to 5s for links to come up */
+ for (i = 0; i < 5; ++i) {
+ if (ipv6)
+ up = !system("ip netns exec " NS0 " ping -6 -c 1 -W 1 " VETH1_ADDR6 " &>/dev/null");
+ else
+ up = !system("ip netns exec " NS0 " ping -c 1 -W 1 " VETH1_ADDR " &>/dev/null");
+
+ if (up)
+ break;
+ }
+
+ return 0;
+fail:
+ return -1;
+}
+
+static void cleanup_topology(void)
+{
+ SYS_NOFAIL("test -f /var/run/netns/" NS0 " && ip netns delete " NS0);
+ SYS_NOFAIL("test -f /var/run/netns/" NS1 " && ip netns delete " NS1);
+}
+
+static int attach(struct ip_check_defrag *skel, bool ipv6)
+{
+ LIBBPF_OPTS(bpf_netfilter_opts, opts,
+ .pf = ipv6 ? NFPROTO_IPV6 : NFPROTO_IPV4,
+ .priority = 42,
+ .flags = BPF_F_NETFILTER_IP_DEFRAG);
+ struct nstoken *nstoken;
+ int err = -1;
+
+ nstoken = open_netns(NS1);
+
+ skel->links.defrag = bpf_program__attach_netfilter(skel->progs.defrag, &opts);
+ if (!ASSERT_OK_PTR(skel->links.defrag, "program attach"))
+ goto out;
+
+ err = 0;
+out:
+ close_netns(nstoken);
+ return err;
+}
+
+static int send_frags(int client)
+{
+ struct sockaddr_storage saddr;
+ struct sockaddr *saddr_p;
+ socklen_t saddr_len;
+ int err;
+
+ saddr_p = (struct sockaddr *)&saddr;
+ err = make_sockaddr(AF_INET, VETH1_ADDR, SERVER_PORT, &saddr, &saddr_len);
+ if (!ASSERT_OK(err, "make_sockaddr"))
+ return -1;
+
+ err = sendto(client, frag_0, sizeof(frag_0), 0, saddr_p, saddr_len);
+ if (!ASSERT_GE(err, 0, "sendto frag_0"))
+ return -1;
+
+ err = sendto(client, frag_1, sizeof(frag_1), 0, saddr_p, saddr_len);
+ if (!ASSERT_GE(err, 0, "sendto frag_1"))
+ return -1;
+
+ err = sendto(client, frag_2, sizeof(frag_2), 0, saddr_p, saddr_len);
+ if (!ASSERT_GE(err, 0, "sendto frag_2"))
+ return -1;
+
+ return 0;
+}
+
+static int send_frags6(int client)
+{
+ struct sockaddr_storage saddr;
+ struct sockaddr *saddr_p;
+ socklen_t saddr_len;
+ int err;
+
+ saddr_p = (struct sockaddr *)&saddr;
+ /* Port needs to be set to 0 for raw ipv6 socket for some reason */
+ err = make_sockaddr(AF_INET6, VETH1_ADDR6, 0, &saddr, &saddr_len);
+ if (!ASSERT_OK(err, "make_sockaddr"))
+ return -1;
+
+ err = sendto(client, frag6_0, sizeof(frag6_0), 0, saddr_p, saddr_len);
+ if (!ASSERT_GE(err, 0, "sendto frag6_0"))
+ return -1;
+
+ err = sendto(client, frag6_1, sizeof(frag6_1), 0, saddr_p, saddr_len);
+ if (!ASSERT_GE(err, 0, "sendto frag6_1"))
+ return -1;
+
+ err = sendto(client, frag6_2, sizeof(frag6_2), 0, saddr_p, saddr_len);
+ if (!ASSERT_GE(err, 0, "sendto frag6_2"))
+ return -1;
+
+ return 0;
+}
+
+void test_bpf_ip_check_defrag_ok(bool ipv6)
+{
+ struct network_helper_opts rx_opts = {
+ .timeout_ms = 1000,
+ .noconnect = true,
+ };
+ struct network_helper_opts tx_ops = {
+ .timeout_ms = 1000,
+ .type = SOCK_RAW,
+ .proto = IPPROTO_RAW,
+ .noconnect = true,
+ };
+ struct sockaddr_storage caddr;
+ struct ip_check_defrag *skel;
+ struct nstoken *nstoken;
+ int client_tx_fd = -1;
+ int client_rx_fd = -1;
+ socklen_t caddr_len;
+ int srv_fd = -1;
+ char buf[1024];
+ int len, err;
+
+ skel = ip_check_defrag__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel_open"))
+ return;
+
+ if (!ASSERT_OK(setup_topology(ipv6), "setup_topology"))
+ goto out;
+
+ if (!ASSERT_OK(attach(skel, ipv6), "attach"))
+ goto out;
+
+ /* Start server in ns1 */
+ nstoken = open_netns(NS1);
+ if (!ASSERT_OK_PTR(nstoken, "setns ns1"))
+ goto out;
+ srv_fd = start_server(ipv6 ? AF_INET6 : AF_INET, SOCK_DGRAM, NULL, SERVER_PORT, 0);
+ close_netns(nstoken);
+ if (!ASSERT_GE(srv_fd, 0, "start_server"))
+ goto out;
+
+ /* Open tx raw socket in ns0 */
+ nstoken = open_netns(NS0);
+ if (!ASSERT_OK_PTR(nstoken, "setns ns0"))
+ goto out;
+ client_tx_fd = connect_to_fd_opts(srv_fd, &tx_ops);
+ close_netns(nstoken);
+ if (!ASSERT_GE(client_tx_fd, 0, "connect_to_fd_opts"))
+ goto out;
+
+ /* Open rx socket in ns0 */
+ nstoken = open_netns(NS0);
+ if (!ASSERT_OK_PTR(nstoken, "setns ns0"))
+ goto out;
+ client_rx_fd = connect_to_fd_opts(srv_fd, &rx_opts);
+ close_netns(nstoken);
+ if (!ASSERT_GE(client_rx_fd, 0, "connect_to_fd_opts"))
+ goto out;
+
+ /* Bind rx socket to a premeditated port */
+ memset(&caddr, 0, sizeof(caddr));
+ nstoken = open_netns(NS0);
+ if (!ASSERT_OK_PTR(nstoken, "setns ns0"))
+ goto out;
+ if (ipv6) {
+ struct sockaddr_in6 *c = (struct sockaddr_in6 *)&caddr;
+
+ c->sin6_family = AF_INET6;
+ inet_pton(AF_INET6, VETH0_ADDR6, &c->sin6_addr);
+ c->sin6_port = htons(CLIENT_PORT);
+ err = bind(client_rx_fd, (struct sockaddr *)c, sizeof(*c));
+ } else {
+ struct sockaddr_in *c = (struct sockaddr_in *)&caddr;
+
+ c->sin_family = AF_INET;
+ inet_pton(AF_INET, VETH0_ADDR, &c->sin_addr);
+ c->sin_port = htons(CLIENT_PORT);
+ err = bind(client_rx_fd, (struct sockaddr *)c, sizeof(*c));
+ }
+ close_netns(nstoken);
+ if (!ASSERT_OK(err, "bind"))
+ goto out;
+
+ /* Send message in fragments */
+ if (ipv6) {
+ if (!ASSERT_OK(send_frags6(client_tx_fd), "send_frags6"))
+ goto out;
+ } else {
+ if (!ASSERT_OK(send_frags(client_tx_fd), "send_frags"))
+ goto out;
+ }
+
+ if (!ASSERT_EQ(skel->bss->shootdowns, 0, "shootdowns"))
+ goto out;
+
+ /* Receive reassembled msg on server and echo back to client */
+ len = recvfrom(srv_fd, buf, sizeof(buf), 0, (struct sockaddr *)&caddr, &caddr_len);
+ if (!ASSERT_GE(len, 0, "server recvfrom"))
+ goto out;
+ len = sendto(srv_fd, buf, len, 0, (struct sockaddr *)&caddr, caddr_len);
+ if (!ASSERT_GE(len, 0, "server sendto"))
+ goto out;
+
+ /* Expect reassembed message to be echoed back */
+ len = recvfrom(client_rx_fd, buf, sizeof(buf), 0, NULL, NULL);
+ if (!ASSERT_EQ(len, sizeof(MAGIC_MESSAGE) - 1, "client short read"))
+ goto out;
+
+out:
+ if (client_rx_fd != -1)
+ close(client_rx_fd);
+ if (client_tx_fd != -1)
+ close(client_tx_fd);
+ if (srv_fd != -1)
+ close(srv_fd);
+ cleanup_topology();
+ ip_check_defrag__destroy(skel);
+}
+
+void test_bpf_ip_check_defrag(void)
+{
+ if (test__start_subtest("v4"))
+ test_bpf_ip_check_defrag_ok(false);
+ if (test__start_subtest("v6"))
+ test_bpf_ip_check_defrag_ok(true);
+}
new file mode 100644
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+#include "bpf_tracing_net.h"
+
+#define NF_DROP 0
+#define NF_ACCEPT 1
+#define ETH_P_IP 0x0800
+#define ETH_P_IPV6 0x86DD
+#define IP_MF 0x2000
+#define IP_OFFSET 0x1FFF
+#define NEXTHDR_FRAGMENT 44
+
+extern int bpf_dynptr_from_skb(struct sk_buff *skb, __u64 flags,
+ struct bpf_dynptr *ptr__uninit) __ksym;
+extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, uint32_t offset,
+ void *buffer, uint32_t buffer__sz) __ksym;
+
+volatile int shootdowns = 0;
+
+static bool is_frag_v4(struct iphdr *iph)
+{
+ int offset;
+ int flags;
+
+ offset = bpf_ntohs(iph->frag_off);
+ flags = offset & ~IP_OFFSET;
+ offset &= IP_OFFSET;
+ offset <<= 3;
+
+ return (flags & IP_MF) || offset;
+}
+
+static bool is_frag_v6(struct ipv6hdr *ip6h)
+{
+ /* Simplifying assumption that there are no extension headers
+ * between fixed header and fragmentation header. This assumption
+ * is only valid in this test case. It saves us the hassle of
+ * searching all potential extension headers.
+ */
+ return ip6h->nexthdr == NEXTHDR_FRAGMENT;
+}
+
+static int handle_v4(struct sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+ u8 iph_buf[20] = {};
+ struct iphdr *iph;
+
+ if (bpf_dynptr_from_skb(skb, 0, &ptr))
+ return NF_DROP;
+
+ iph = bpf_dynptr_slice(&ptr, 0, iph_buf, sizeof(iph_buf));
+ if (!iph)
+ return NF_DROP;
+
+ /* Shootdown any frags */
+ if (is_frag_v4(iph)) {
+ shootdowns++;
+ return NF_DROP;
+ }
+
+ return NF_ACCEPT;
+}
+
+static int handle_v6(struct sk_buff *skb)
+{
+ struct bpf_dynptr ptr;
+ struct ipv6hdr *ip6h;
+ u8 ip6h_buf[40] = {};
+
+ if (bpf_dynptr_from_skb(skb, 0, &ptr))
+ return NF_DROP;
+
+ ip6h = bpf_dynptr_slice(&ptr, 0, ip6h_buf, sizeof(ip6h_buf));
+ if (!ip6h)
+ return NF_DROP;
+
+ /* Shootdown any frags */
+ if (is_frag_v6(ip6h)) {
+ shootdowns++;
+ return NF_DROP;
+ }
+
+ return NF_ACCEPT;
+}
+
+SEC("netfilter")
+int defrag(struct bpf_nf_ctx *ctx)
+{
+ struct sk_buff *skb = ctx->skb;
+
+ switch (bpf_ntohs(skb->protocol)) {
+ case ETH_P_IP:
+ return handle_v4(skb);
+ case ETH_P_IPV6:
+ return handle_v6(skb);
+ default:
+ return NF_ACCEPT;
+ }
+}
+
+char _license[] SEC("license") = "GPL";