This selftest tests 2 major scenarios: the BPF based defragmentation can succesfully be done and that packet pointers are invalidated after calls to the kfunc.

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 --- .../selftests/bpf/generate_udp_fragments.py | 52 +++ .../bpf/prog_tests/ip_check_defrag.c | 296 ++++++++++++++++++ .../selftests/bpf/progs/bpf_tracing_net.h | 1 + .../selftests/bpf/progs/ip_check_defrag.c | 83 +++++ 4 files changed, 432 insertions(+) create mode 100755 tools/testing/selftests/bpf/generate_udp_fragments.py 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/generate_udp_fragments.py b/tools/testing/selftests/bpf/generate_udp_fragments.py new file mode 100755 index 000000000000..b7ee3f7b42b4 --- /dev/null +++ b/tools/testing/selftests/bpf/generate_udp_fragments.py @@ -0,0 +1,52 @@ +#!/bin/env python3 + +""" +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 valid C code. +""" + +import argparse +from scapy.all import * + +def print_frags(frags): + 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] + + print(f"static uint8_t frag{idx}[] = {{") + for chunk in chunks_fmted: + print(f"\t{chunk},") + print(f"}};") + + +def main(args): + # srcip of 0 is filled in by IP_HDRINCL + sip = "0.0.0.0" + dip = args.dst_ip + sport = args.src_port + dport = args.dst_port + payload = args.payload.encode() + + # Disable UDP checksums to keep code simpler + pkt = IP(src=sip,dst=dip) / UDP(sport=sport,dport=dport,chksum=0) / Raw(load=payload) + + frags = [f.build() for f in pkt.fragment(24)] + print_frags(frags) + + +if __name__ == "__main__": + parser = argparse.ArgumentParser() + parser.add_argument("dst_ip") + parser.add_argument("src_port", type=int) + parser.add_argument("dst_port", type=int) + parser.add_argument("payload") + args = parser.parse_args() + + main(args) 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..ed078e8265de --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/ip_check_defrag.c @@ -0,0 +1,296 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <test_progs.h> +#include <net/if.h> +#include <network_helpers.h> +#include "ip_check_defrag.skel.h" + +/* + * This selftest spins up a client and an echo server, each in their own + * network namespace. The server will receive fragmented messages which + * the attached BPF prog should reassemble. We verify that reassembly + * occurred by checking the original (fragmented) message is received + * in whole. + * + * 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 VETH1_ADDR "172.16.1.200" +#define CLIENT_PORT 48878 +#define SERVER_PORT 48879 +#define MAGIC_MESSAGE "THIS IS THE ORIGINAL MESSAGE, PLEASE REASSEMBLE ME" + +static char log_buf[1024 * 1024]; + +#define SYS(fmt, ...) \ + ({ \ + char cmd[1024]; \ + snprintf(cmd, sizeof(cmd), fmt, ##__VA_ARGS__); \ + if (!ASSERT_OK(system(cmd), cmd)) \ + goto fail; \ + }) + +#define SYS_NOFAIL(fmt, ...) \ + ({ \ + char cmd[1024]; \ + snprintf(cmd, sizeof(cmd), fmt, ##__VA_ARGS__); \ + system(cmd); \ + }) + +/* + * The following fragments are generated with this script invocation: + * + * ./generate_udp_fragments $VETH1_ADDR $CLIENT_PORT $SERVER_PORT $MAGIC_MESSAGE + * + * where the `$` indicates replacement with preprocessor macro. + */ +static uint8_t frag0[] = { + 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 frag1[] = { + 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 frag2[] = { + 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 int setup_topology(void) +{ + SYS("ip netns add " NS0); + SYS("ip netns add " NS1); + SYS("ip link add " VETH0 " netns " NS0 " type veth peer name " VETH1 " netns " NS1); + SYS("ip -net " NS0 " addr add " VETH0_ADDR "/24 dev " VETH0); + SYS("ip -net " NS0 " link set dev " VETH0 " up"); + SYS("ip -net " NS1 " addr add " VETH1_ADDR "/24 dev " VETH1); + SYS("ip -net " NS1 " link set dev " VETH1 " up"); + + 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) +{ + LIBBPF_OPTS(bpf_tc_hook, tc_hook, + .attach_point = BPF_TC_INGRESS); + LIBBPF_OPTS(bpf_tc_opts, tc_attach, + .prog_fd = bpf_program__fd(skel->progs.defrag)); + struct nstoken *nstoken; + int err = -1; + + nstoken = open_netns(NS1); + + tc_hook.ifindex = if_nametoindex(VETH1); + if (!ASSERT_OK(bpf_tc_hook_create(&tc_hook), "bpf_tc_hook_create")) + goto out; + + if (!ASSERT_OK(bpf_tc_attach(&tc_hook, &tc_attach), "bpf_tc_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, frag0, sizeof(frag0), 0, saddr_p, saddr_len); + if (!ASSERT_GE(err, 0, "sendto frag0")) + return -1; + + err = sendto(client, frag1, sizeof(frag1), 0, saddr_p, saddr_len); + if (!ASSERT_GE(err, 0, "sendto frag1")) + return -1; + + err = sendto(client, frag2, sizeof(frag2), 0, saddr_p, saddr_len); + if (!ASSERT_GE(err, 0, "sendto frag2")) + return -1; + + return 0; +} + +void test_bpf_ip_check_defrag_ok(void) +{ + 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 ip_check_defrag *skel; + struct sockaddr_in caddr; + 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(), "setup_topology")) + goto out; + + if (!ASSERT_OK(attach(skel), "attach")) + goto out; + + /* Start server in ns1 */ + nstoken = open_netns(NS1); + if (!ASSERT_OK_PTR(nstoken, "setns ns1")) + goto out; + srv_fd = start_server(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)); + caddr.sin_family = AF_INET; + inet_pton(AF_INET, VETH0_ADDR, &caddr.sin_addr); + caddr.sin_port = htons(CLIENT_PORT); + nstoken = open_netns(NS0); + err = bind(client_rx_fd, (struct sockaddr *)&caddr, sizeof(caddr)); + close_netns(nstoken); + if (!ASSERT_OK(err, "bind")) + goto out; + + /* Send message in fragments */ + if (!ASSERT_OK(send_frags(client_tx_fd), "send_frags")) + goto out; + + if (!ASSERT_EQ(skel->bss->frags_seen, 3, "frags_seen")) + goto out; + + if (!ASSERT_FALSE(skel->data->is_final_frag, "is_final_frag")) + 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_fail(void) +{ + const char *err_msg = "invalid mem access 'scalar'"; + LIBBPF_OPTS(bpf_object_open_opts, opts, + .kernel_log_buf = log_buf, + .kernel_log_size = sizeof(log_buf), + .kernel_log_level = 1); + struct ip_check_defrag *skel; + struct bpf_program *prog; + int err; + + skel = ip_check_defrag__open_opts(&opts); + if (!ASSERT_OK_PTR(skel, "ip_check_defrag__open_opts")) + return; + + prog = bpf_object__find_program_by_name(skel->obj, "defrag_fail"); + if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name")) + goto out; + + bpf_program__set_autoload(prog, true); + + err = ip_check_defrag__load(skel); + if (!ASSERT_ERR(err, "ip_check_defrag__load must fail")) + goto out; + + if (!ASSERT_OK_PTR(strstr(log_buf, err_msg), "expected error message")) { + fprintf(stderr, "Expected: %s\n", err_msg); + fprintf(stderr, "Verifier: %s\n", log_buf); + } + +out: + ip_check_defrag__destroy(skel); +} + +void test_bpf_ip_check_defrag(void) +{ + if (test__start_subtest("ok")) + test_bpf_ip_check_defrag_ok(); + if (test__start_subtest("fail")) + test_bpf_ip_check_defrag_fail(); +} diff --git a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h index b394817126cf..a1d6cc1f2ef8 100644 --- a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h +++ b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h @@ -26,6 +26,7 @@ #define IPV6_AUTOFLOWLABEL 70

#define TC_ACT_UNSPEC (-1) +#define TC_ACT_OK 0 #define TC_ACT_SHOT 2

#define SOL_TCP 6 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..71300b77a43f --- /dev/null +++ b/tools/testing/selftests/bpf/progs/ip_check_defrag.c @@ -0,0 +1,83 @@ +// 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 ETH_P_IP 0x0800 +#define IP_DF 0x4000 +#define IP_MF 0x2000 +#define IP_OFFSET 0x1FFF +#define ctx_ptr(field) (void *)(long)(field) + +int bpf_ip_check_defrag(struct __sk_buff *ctx, u64 netns) __ksym; + +volatile int frags_seen = 0; +volatile bool is_final_frag = true; + +static inline bool is_frag(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; +} + +SEC("tc") +int defrag(struct __sk_buff *skb) +{ + void *data_end = ctx_ptr(skb->data_end); + void *data = ctx_ptr(skb->data); + struct iphdr *iph; + + if (skb->protocol != bpf_htons(ETH_P_IP)) + return TC_ACT_OK; + + iph = data + sizeof(struct ethhdr); + if (iph + 1 > data_end) + return TC_ACT_SHOT; + + if (!is_frag(iph)) + return TC_ACT_OK; + + frags_seen++; + if (bpf_ip_check_defrag(skb, BPF_F_CURRENT_NETNS)) + return TC_ACT_SHOT; + + data_end = ctx_ptr(skb->data_end); + data = ctx_ptr(skb->data); + iph = data + sizeof(struct ethhdr); + if (iph + 1 > data_end) + return TC_ACT_SHOT; + is_final_frag = is_frag(iph); + + return TC_ACT_OK; +} + +SEC("?tc") +int defrag_fail(struct __sk_buff *skb) +{ + void *data_end = ctx_ptr(skb->data_end); + void *data = ctx_ptr(skb->data); + struct iphdr *iph; + + if (skb->protocol != bpf_htons(ETH_P_IP)) + return TC_ACT_OK; + + iph = data + sizeof(struct ethhdr); + if (iph + 1 > data_end) + return TC_ACT_SHOT; + + if (bpf_ip_check_defrag(skb, BPF_F_CURRENT_NETNS)) + return TC_ACT_SHOT; + + /* Boom. Must revalidate pkt ptrs */ + return iph->ttl ? TC_ACT_OK : TC_ACT_SHOT; +} + +char _license[] SEC("license") = "GPL";