=== Context ===
In the context of a middlebox, fragmented packets are tricky to handle. The full 5-tuple of a packet is often only available in the first fragment which makes enforcing consistent policy difficult. There are really only two stateless options, neither of which are very nice:
1. Enforce policy on first fragment and accept all subsequent fragments. This works but may let in certain attacks or allow data exfiltration.
2. Enforce policy on first fragment and drop all subsequent fragments. This does not really work b/c some protocols may rely on fragmentation. For example, DNS may rely on oversized UDP packets for large responses.
So stateful tracking is the only sane option. RFC 8900 [0] calls this out as well in section 6.3:
Middleboxes [...] should process IP fragments in a manner that is consistent with [RFC0791] and [RFC8200]. In many cases, middleboxes must maintain state in order to achieve this goal.
=== BPF related bits ===
Policy has traditionally been enforced from XDP/TC hooks. Both hooks run before kernel reassembly facilities. However, with the new BPF_PROG_TYPE_NETFILTER, we can rather easily hook into existing netfilter reassembly infra.
The basic idea is we bump a refcnt on the netfilter defrag module and then run the bpf prog after the defrag module runs. This allows bpf progs to transparently see full, reassembled packets. The nice thing about this is that progs don't have to carry around logic to detect fragments.
=== Changelog ===
Changes from v1:
* Drop bpf_program__attach_netfilter() patches * static -> static const where appropriate * Fix callback assignment order during registration * Only request_module() if callbacks are missing * Fix retval when modprobe fails in userspace * Fix v6 defrag module name (nf_defrag_ipv6_hooks -> nf_defrag_ipv6) * Simplify priority checking code * Add warning if module doesn't assign callbacks in the future * Take refcnt on module while defrag link is active
[0]: https://datatracker.ietf.org/doc/html/rfc8900
Daniel Xu (6): netfilter: defrag: Add glue hooks for enabling/disabling defrag netfilter: bpf: Support BPF_F_NETFILTER_IP_DEFRAG in netfilter link netfilter: bpf: Prevent defrag module unload while link active bpf: selftests: Support not connecting client socket bpf: selftests: Support custom type and proto for client sockets bpf: selftests: Add defrag selftests
include/linux/netfilter.h | 15 + include/uapi/linux/bpf.h | 5 + net/ipv4/netfilter/nf_defrag_ipv4.c | 17 +- net/ipv6/netfilter/nf_defrag_ipv6_hooks.c | 11 + net/netfilter/core.c | 6 + net/netfilter/nf_bpf_link.c | 149 ++++++++- tools/include/uapi/linux/bpf.h | 5 + tools/testing/selftests/bpf/Makefile | 4 +- .../selftests/bpf/generate_udp_fragments.py | 90 ++++++ .../selftests/bpf/ip_check_defrag_frags.h | 57 ++++ tools/testing/selftests/bpf/network_helpers.c | 26 +- tools/testing/selftests/bpf/network_helpers.h | 3 + .../bpf/prog_tests/ip_check_defrag.c | 282 ++++++++++++++++++ .../selftests/bpf/progs/ip_check_defrag.c | 104 +++++++ 14 files changed, 752 insertions(+), 22 deletions(-) create mode 100755 tools/testing/selftests/bpf/generate_udp_fragments.py create mode 100644 tools/testing/selftests/bpf/ip_check_defrag_frags.h create mode 100644 tools/testing/selftests/bpf/prog_tests/ip_check_defrag.c create mode 100644 tools/testing/selftests/bpf/progs/ip_check_defrag.c
For connectionless protocols or raw sockets we do not want to actually connect() to the server.
Signed-off-by: Daniel Xu dxu@dxuuu.xyz --- tools/testing/selftests/bpf/network_helpers.c | 5 +++-- tools/testing/selftests/bpf/network_helpers.h | 1 + 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c index a105c0cd008a..d5c78c08903b 100644 --- a/tools/testing/selftests/bpf/network_helpers.c +++ b/tools/testing/selftests/bpf/network_helpers.c @@ -301,8 +301,9 @@ int connect_to_fd_opts(int server_fd, const struct network_helper_opts *opts) strlen(opts->cc) + 1)) goto error_close;
- if (connect_fd_to_addr(fd, &addr, addrlen, opts->must_fail)) - goto error_close; + if (!opts->noconnect) + if (connect_fd_to_addr(fd, &addr, addrlen, opts->must_fail)) + goto error_close;
return fd;
diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h index 694185644da6..87894dc984dd 100644 --- a/tools/testing/selftests/bpf/network_helpers.h +++ b/tools/testing/selftests/bpf/network_helpers.h @@ -21,6 +21,7 @@ struct network_helper_opts { const char *cc; int timeout_ms; bool must_fail; + bool noconnect; };
/* ipv4 test vector */
Extend connect_to_fd_opts() to take optional type and protocol parameters for the client socket. These parameters are useful when opening a raw socket to send IP fragments.
Signed-off-by: Daniel Xu dxu@dxuuu.xyz --- tools/testing/selftests/bpf/network_helpers.c | 21 +++++++++++++------ tools/testing/selftests/bpf/network_helpers.h | 2 ++ 2 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c index d5c78c08903b..910d5d0470e6 100644 --- a/tools/testing/selftests/bpf/network_helpers.c +++ b/tools/testing/selftests/bpf/network_helpers.c @@ -270,14 +270,23 @@ int connect_to_fd_opts(int server_fd, const struct network_helper_opts *opts) opts = &default_opts;
optlen = sizeof(type); - if (getsockopt(server_fd, SOL_SOCKET, SO_TYPE, &type, &optlen)) { - log_err("getsockopt(SOL_TYPE)"); - return -1; + + if (opts->type) { + type = opts->type; + } else { + if (getsockopt(server_fd, SOL_SOCKET, SO_TYPE, &type, &optlen)) { + log_err("getsockopt(SOL_TYPE)"); + return -1; + } }
- if (getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen)) { - log_err("getsockopt(SOL_PROTOCOL)"); - return -1; + if (opts->proto) { + protocol = opts->proto; + } else { + if (getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen)) { + log_err("getsockopt(SOL_PROTOCOL)"); + return -1; + } }
addrlen = sizeof(addr); diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h index 87894dc984dd..5eccc67d1a99 100644 --- a/tools/testing/selftests/bpf/network_helpers.h +++ b/tools/testing/selftests/bpf/network_helpers.h @@ -22,6 +22,8 @@ struct network_helper_opts { int timeout_ms; bool must_fail; bool noconnect; + int type; + int proto; };
/* ipv4 test vector */
These selftests tests 2 major scenarios: the BPF based defragmentation can successfully be done and that packet pointers are invalidated after calls to the kfunc. The logic is similar for both ipv4 and ipv6.
In the first scenario, we create a UDP client and UDP echo server. The the server side is fairly straightforward: we attach the prog and simply echo back the message.
The on the client side, we send fragmented packets to and expect the reassembled message back from the server.
Signed-off-by: Daniel Xu dxu@dxuuu.xyz --- tools/testing/selftests/bpf/Makefile | 4 +- .../selftests/bpf/generate_udp_fragments.py | 90 ++++++ .../selftests/bpf/ip_check_defrag_frags.h | 57 ++++ .../bpf/prog_tests/ip_check_defrag.c | 282 ++++++++++++++++++ .../selftests/bpf/progs/ip_check_defrag.c | 104 +++++++ 5 files changed, 535 insertions(+), 2 deletions(-) create mode 100755 tools/testing/selftests/bpf/generate_udp_fragments.py create mode 100644 tools/testing/selftests/bpf/ip_check_defrag_frags.h create mode 100644 tools/testing/selftests/bpf/prog_tests/ip_check_defrag.c create mode 100644 tools/testing/selftests/bpf/progs/ip_check_defrag.c
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 882be03b179f..619df497fce5 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -565,8 +565,8 @@ 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 \ diff --git a/tools/testing/selftests/bpf/generate_udp_fragments.py b/tools/testing/selftests/bpf/generate_udp_fragments.py new file mode 100755 index 000000000000..2b8a1187991c --- /dev/null +++ b/tools/testing/selftests/bpf/generate_udp_fragments.py @@ -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) diff --git a/tools/testing/selftests/bpf/ip_check_defrag_frags.h b/tools/testing/selftests/bpf/ip_check_defrag_frags.h new file mode 100644 index 000000000000..70ab7e9fa22b --- /dev/null +++ b/tools/testing/selftests/bpf/ip_check_defrag_frags.h @@ -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 */ diff --git a/tools/testing/selftests/bpf/prog_tests/ip_check_defrag.c b/tools/testing/selftests/bpf/prog_tests/ip_check_defrag.c new file mode 100644 index 000000000000..5cd08d6e0ebc --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/ip_check_defrag.c @@ -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); +} diff --git a/tools/testing/selftests/bpf/progs/ip_check_defrag.c b/tools/testing/selftests/bpf/progs/ip_check_defrag.c new file mode 100644 index 000000000000..4259c6d59968 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/ip_check_defrag.c @@ -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";
On Thu, Jul 06, 2023 at 05:25:53PM -0600, Daniel Xu wrote:
+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);
imo the end results is pretty neat. The users would just add this flag and netfilter bpf prog will see reassembled packets.
The patches look good to me.
Florian, could you please review/ack, so we can pull them in?
linux-kselftest-mirror@lists.linaro.org
-
Alexei Starovoitov -
Daniel Xu