As is described in the "How to use MPTCP?" section in MPTCP wiki [1]: "Your app can create sockets with IPPROTO_MPTCP as the proto: ( socket(AF_INET, SOCK_STREAM, IPPROTO_MPTCP); ). Legacy apps can be forced to create and use MPTCP sockets instead of TCP ones via the mptcpize command bundled with the mptcpd daemon." But the mptcpize (LD_PRELOAD technique) command has some limitations [2]: - it doesn't work if the application is not using libc (e.g. GoLang apps) - in some envs, it might not be easy to set env vars / change the way apps are launched, e.g. on Android - mptcpize needs to be launched with all apps that want MPTCP: we could have more control from BPF to enable MPTCP only for some apps or all the ones of a netns or a cgroup, etc. - it is not in BPF, we cannot talk about it at netdev conf. So this patchset attempts to use BPF to implement functions similer to mptcpize. The main idea is add a hook in sys_socket() to change the protocol id from IPPROTO_TCP (or 0) to IPPROTO_MPTCP. [1] https://github.com/multipath-tcp/mptcp_net-next/wiki [2] https://github.com/multipath-tcp/mptcp_net-next/issues/79 v6: - add update_socket_protocol. v5: - add bpf_mptcpify helper. v4: - use lsm_cgroup/socket_create v3: - patch 8: char cmd[128]; -> char cmd[256]; v2: - Fix build selftests errors reported by CI Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/79 Signed-off-by: Geliang Tang <geliang.tang@xxxxxxxx> --- net/mptcp/bpf.c | 17 +++ net/socket.c | 6 + .../testing/selftests/bpf/prog_tests/mptcp.c | 126 ++++++++++++++++-- tools/testing/selftests/bpf/progs/mptcpify.c | 26 ++++ 4 files changed, 166 insertions(+), 9 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c index 5a0a84ad94af..c43aee31014d 100644 --- a/net/mptcp/bpf.c +++ b/net/mptcp/bpf.c @@ -12,6 +12,23 @@ #include <linux/bpf.h> #include "protocol.h" +#ifdef CONFIG_BPF_JIT +BTF_SET8_START(bpf_mptcp_fmodret_ids) +BTF_ID_FLAGS(func, update_socket_protocol) +BTF_SET8_END(bpf_mptcp_fmodret_ids) + +static const struct btf_kfunc_id_set bpf_mptcp_fmodret_set = { + .owner = THIS_MODULE, + .set = &bpf_mptcp_fmodret_ids, +}; + +static int __init bpf_mptcp_kfunc_init(void) +{ + return register_btf_fmodret_id_set(&bpf_mptcp_fmodret_set); +} +late_initcall(bpf_mptcp_kfunc_init); +#endif /* CONFIG_BPF_JIT */ + struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk) { if (sk && sk_fullsock(sk) && sk->sk_protocol == IPPROTO_TCP && sk_is_mptcp(sk)) diff --git a/net/socket.c b/net/socket.c index 2b0e54b2405c..4c7b2ff711f0 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1644,11 +1644,17 @@ struct file *__sys_socket_file(int family, int type, int protocol) return sock_alloc_file(sock, flags, NULL); } +noinline int update_socket_protocol(int family, int type, int protocol) +{ + return protocol; +} + int __sys_socket(int family, int type, int protocol) { struct socket *sock; int flags; + protocol = update_socket_protocol(family, type, protocol); sock = __sys_socket_create(family, type, protocol); if (IS_ERR(sock)) return PTR_ERR(sock); diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c index cd0c42fff7c0..ffa98d5c46af 100644 --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c @@ -6,8 +6,9 @@ #include "cgroup_helpers.h" #include "network_helpers.h" #include "mptcp_sock.skel.h" +#include "mptcpify.skel.h" -#define NS_TEST "mptcp_ns" +char NS_TEST[32]; #ifndef TCP_CA_NAME_MAX #define TCP_CA_NAME_MAX 16 @@ -22,6 +23,26 @@ struct mptcp_storage { char ca_name[TCP_CA_NAME_MAX]; }; +static struct nstoken *create_netns(void) +{ + srand(time(NULL)); + snprintf(NS_TEST, sizeof(NS_TEST), "mptcp_ns_%d", rand()); + SYS(fail, "ip netns add %s", NS_TEST); + SYS(fail, "ip -net %s link set dev lo up", NS_TEST); + + return open_netns(NS_TEST); +fail: + return NULL; +} + +static void cleanup_netns(struct nstoken *nstoken) +{ + if (nstoken) + close_netns(nstoken); + + SYS_NOFAIL("ip netns del %s &> /dev/null", NS_TEST); +} + static int verify_tsk(int map_fd, int client_fd) { int err, cfd = client_fd; @@ -147,11 +168,8 @@ static void test_base(void) if (!ASSERT_GE(cgroup_fd, 0, "test__join_cgroup")) return; - SYS(fail, "ip netns add %s", NS_TEST); - SYS(fail, "ip -net %s link set dev lo up", NS_TEST); - - nstoken = open_netns(NS_TEST); - if (!ASSERT_OK_PTR(nstoken, "open_netns")) + nstoken = create_netns(); + if (!ASSERT_OK_PTR(nstoken, "create_netns")) goto fail; /* without MPTCP */ @@ -174,11 +192,99 @@ static void test_base(void) close(server_fd); fail: - if (nstoken) - close_netns(nstoken); + cleanup_netns(nstoken); - SYS_NOFAIL("ip netns del " NS_TEST " &> /dev/null"); + close(cgroup_fd); +} + +static void send_byte(int fd) +{ + char b = 0x55; + + ASSERT_EQ(write(fd, &b, sizeof(b)), 1, "send single byte"); +} + +static int verify_mptcpify(void) +{ + char cmd[256]; + int err = 0; + + snprintf(cmd, sizeof(cmd), + "ip netns exec %s ss -tOni | grep -q '%s'", + NS_TEST, "tcp-ulp-mptcp"); + if (!ASSERT_OK(system(cmd), "No tcp-ulp-mptcp found!")) + err++; + + snprintf(cmd, sizeof(cmd), + "ip netns exec %s nstat -asz %s | awk '%s' | grep -q '%s'", + NS_TEST, "MPTcpExtMPCapableSYNACKRX", + "NR==1 {next} {print $2}", "1"); + if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!")) + err++; + + return err; +} + +static int run_mptcpify(int cgroup_fd) +{ + int server_fd, client_fd, prog_fd, err = 0; + struct mptcpify *mptcpify_skel; + + mptcpify_skel = mptcpify__open_and_load(); + if (!ASSERT_OK_PTR(mptcpify_skel, "skel_open_load")) + return -EIO; + err = mptcpify__attach(mptcpify_skel); + if (!ASSERT_OK(err, "skel_attach")) + goto out; + + prog_fd = bpf_program__fd(mptcpify_skel->progs.mptcpify); + if (!ASSERT_GE(prog_fd, 0, "bpf_program__fd")) { + err = -EIO; + goto out; + } + + /* without MPTCP */ + server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0); + if (!ASSERT_GE(server_fd, 0, "start_server")) { + err = -EIO; + goto out; + } + + client_fd = connect_to_fd(server_fd, 0); + if (!ASSERT_GE(client_fd, 0, "connect to fd")) { + err = -EIO; + goto close_server; + } + + send_byte(client_fd); + err += verify_mptcpify(); + + close(client_fd); +close_server: + close(server_fd); +out: + mptcpify__destroy(mptcpify_skel); + return err; +} + +static void test_mptcpify(void) +{ + struct nstoken *nstoken = NULL; + int cgroup_fd; + + cgroup_fd = test__join_cgroup("/mptcpify"); + if (!ASSERT_GE(cgroup_fd, 0, "test__join_cgroup")) + return; + + nstoken = create_netns(); + if (!ASSERT_OK_PTR(nstoken, "create_netns")) + goto fail; + + ASSERT_OK(run_mptcpify(cgroup_fd), "run_mptcpify"); + +fail: + cleanup_netns(nstoken); close(cgroup_fd); } @@ -186,4 +292,6 @@ void test_mptcp(void) { if (test__start_subtest("base")) test_base(); + if (test__start_subtest("mptcpify")) + test_mptcpify(); } diff --git a/tools/testing/selftests/bpf/progs/mptcpify.c b/tools/testing/selftests/bpf/progs/mptcpify.c new file mode 100644 index 000000000000..c5e5b27ac3df --- /dev/null +++ b/tools/testing/selftests/bpf/progs/mptcpify.c @@ -0,0 +1,26 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023, SUSE. */ + +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include "bpf_tcp_helpers.h" + +char _license[] SEC("license") = "GPL"; + +#define AF_INET 2 +#define AF_INET6 10 +#define SOCK_STREAM 1 +#define IPPROTO_TCP 6 +#define IPPROTO_MPTCP 262 + +SEC("fmod_ret/update_socket_protocol") +int BPF_PROG(mptcpify, int family, int type, int protocol) +{ + if ((family == AF_INET || family == AF_INET6) && + type == SOCK_STREAM && + (!protocol || protocol == IPPROTO_TCP)) { + return IPPROTO_MPTCP; + } + + return protocol; +} -- 2.35.3
