As is described in the "How to use MPTCP?" section in MPTCP wiki [1]:
"Your app should 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 to 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
v13: - drop "Use random netns name for mptcp" patch.
v12: - update diag_* log of update_socket_protocol. - add 'ip netns show' after 'ip netns del' to check if there is a test did not clean up its netns. - return libbpf_get_error() instead of -EIO for the error from open_and_load(). - Use getsockopt(SOL_PROTOCOL) to verify mptcp protocol intead of using 'ss -tOni'.
v11: - add comments about outputs of 'ss' and 'nstat'. - use "err = verify_mptcpify()" instead of using =+.
v10: - drop "#ifdef CONFIG_BPF_JIT". - include vmlinux.h and bpf_tracing_net.h to avoid defining some macros. - drop unneeded checks for mptcp.
v9: - update comment for 'update_socket_protocol'.
v8: - drop the additional checks on the 'protocol' value after the 'update_socket_protocol()' call.
v7: - add __weak and __diag_* for update_socket_protocol.
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
Geliang Tang (4): bpf: Add update_socket_protocol hook selftests/bpf: Add two mptcp netns helpers selftests/bpf: Fix error checks of mptcp open_and_load selftests/bpf: Add mptcpify test
net/mptcp/bpf.c | 15 ++ net/socket.c | 26 +++- .../testing/selftests/bpf/prog_tests/mptcp.c | 141 +++++++++++++++--- tools/testing/selftests/bpf/progs/mptcpify.c | 20 +++ 4 files changed, 182 insertions(+), 20 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c
Add a hook named update_socket_protocol in __sys_socket(), for bpf progs to attach to and update socket protocol. One user case is to force legacy TCP apps to create and use MPTCP sockets instead of TCP ones.
Define a fmod_ret set named bpf_mptcp_fmodret_ids, add the hook update_socket_protocol into this set, and register it in bpf_mptcp_kfunc_init().
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/79 Acked-by: Matthieu Baerts matthieu.baerts@tessares.net Acked-by: Yonghong Song yonghong.song@linux.dev Signed-off-by: Geliang Tang geliang.tang@suse.com --- net/mptcp/bpf.c | 15 +++++++++++++++ net/socket.c | 26 +++++++++++++++++++++++++- 2 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/net/mptcp/bpf.c b/net/mptcp/bpf.c index 5a0a84ad94af..8a16672b94e2 100644 --- a/net/mptcp/bpf.c +++ b/net/mptcp/bpf.c @@ -19,3 +19,18 @@ struct mptcp_sock *bpf_mptcp_sock_from_subflow(struct sock *sk)
return NULL; } + +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); diff --git a/net/socket.c b/net/socket.c index 5d4e37595e9a..fdb5233bf560 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1657,12 +1657,36 @@ struct file *__sys_socket_file(int family, int type, int protocol) return sock_alloc_file(sock, flags, NULL); }
+/* A hook for bpf progs to attach to and update socket protocol. + * + * A static noinline declaration here could cause the compiler to + * optimize away the function. A global noinline declaration will + * keep the definition, but may optimize away the callsite. + * Therefore, __weak is needed to ensure that the call is still + * emitted, by telling the compiler that we don't know what the + * function might eventually be. + * + * __diag_* below are needed to dismiss the missing prototype warning. + */ + +__diag_push(); +__diag_ignore_all("-Wmissing-prototypes", + "A fmod_ret entry point for BPF programs"); + +__weak noinline int update_socket_protocol(int family, int type, int protocol) +{ + return protocol; +} + +__diag_pop(); + int __sys_socket(int family, int type, int protocol) { struct socket *sock; int flags;
- sock = __sys_socket_create(family, type, protocol); + sock = __sys_socket_create(family, type, + update_socket_protocol(family, type, protocol)); if (IS_ERR(sock)) return PTR_ERR(sock);
Add two netns helpers for mptcp tests: create_netns() and cleanup_netns(). Use them in test_base().
These new helpers will be re-used in the following commits introducing new tests.
Acked-by: Yonghong Song yonghong.song@linux.dev Reviewed-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: Geliang Tang geliang.tang@suse.com --- .../testing/selftests/bpf/prog_tests/mptcp.c | 31 +++++++++++++------ 1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c index cd0c42fff7c0..76afb5191772 100644 --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c @@ -22,6 +22,24 @@ struct mptcp_storage { char ca_name[TCP_CA_NAME_MAX]; };
+static struct nstoken *create_netns(void) +{ + 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 +165,8 @@ 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 +189,7 @@ static void test_base(void) close(server_fd);
fail: - if (nstoken) - close_netns(nstoken); - - SYS_NOFAIL("ip netns del " NS_TEST " &> /dev/null"); - + cleanup_netns(nstoken); close(cgroup_fd); }
Return libbpf_get_error(), instead of -EIO, for the error from mptcp_sock__open_and_load().
Load success means prog_fd and map_fd are always valid. So drop these unneeded ASSERT_GE checks for them in mptcp run_test().
Acked-by: Yonghong Song yonghong.song@linux.dev Signed-off-by: Geliang Tang geliang.tang@suse.com --- tools/testing/selftests/bpf/prog_tests/mptcp.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c index 76afb5191772..3d3999067e27 100644 --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c @@ -118,24 +118,14 @@ static int run_test(int cgroup_fd, int server_fd, bool is_mptcp)
sock_skel = mptcp_sock__open_and_load(); if (!ASSERT_OK_PTR(sock_skel, "skel_open_load")) - return -EIO; + return libbpf_get_error(sock_skel);
err = mptcp_sock__attach(sock_skel); if (!ASSERT_OK(err, "skel_attach")) goto out;
prog_fd = bpf_program__fd(sock_skel->progs._sockops); - if (!ASSERT_GE(prog_fd, 0, "bpf_program__fd")) { - err = -EIO; - goto out; - } - map_fd = bpf_map__fd(sock_skel->maps.socket_storage_map); - if (!ASSERT_GE(map_fd, 0, "bpf_map__fd")) { - err = -EIO; - goto out; - } - err = bpf_prog_attach(prog_fd, cgroup_fd, BPF_CGROUP_SOCK_OPS, 0); if (!ASSERT_OK(err, "bpf_prog_attach")) goto out;
Implement a new test program mptcpify: if the family is AF_INET or AF_INET6, the type is SOCK_STREAM, and the protocol ID is 0 or IPPROTO_TCP, set it to IPPROTO_MPTCP. It will be hooked in update_socket_protocol().
Extend the MPTCP test base, add a selftest test_mptcpify() for the mptcpify case. Open and load the mptcpify test prog to mptcpify the TCP sockets dynamically, then use start_server() and connect_to_fd() to create a TCP socket, but actually what's created is an MPTCP socket, which can be verified through 'getsockopt(SOL_PROTOCOL)' and 'nstat' commands.
Acked-by: Yonghong Song yonghong.song@linux.dev Reviewed-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: Geliang Tang geliang.tang@suse.com --- .../testing/selftests/bpf/prog_tests/mptcp.c | 102 ++++++++++++++++++ tools/testing/selftests/bpf/progs/mptcpify.c | 20 ++++ 2 files changed, 122 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/mptcpify.c
diff --git a/tools/testing/selftests/bpf/prog_tests/mptcp.c b/tools/testing/selftests/bpf/prog_tests/mptcp.c index 3d3999067e27..a6bbc734a876 100644 --- a/tools/testing/selftests/bpf/prog_tests/mptcp.c +++ b/tools/testing/selftests/bpf/prog_tests/mptcp.c @@ -2,13 +2,19 @@ /* Copyright (c) 2020, Tessares SA. */ /* Copyright (c) 2022, SUSE. */
+#include <netinet/in.h> #include <test_progs.h> #include "cgroup_helpers.h" #include "network_helpers.h" #include "mptcp_sock.skel.h" +#include "mptcpify.skel.h"
#define NS_TEST "mptcp_ns"
+#ifndef IPPROTO_MPTCP +#define IPPROTO_MPTCP 262 +#endif + #ifndef TCP_CA_NAME_MAX #define TCP_CA_NAME_MAX 16 #endif @@ -183,8 +189,104 @@ static void test_base(void) 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(int server_fd) +{ + socklen_t optlen; + char cmd[256]; + int protocol; + int err = 0; + + optlen = sizeof(protocol); + if (!ASSERT_OK(getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen), + "getsockopt(SOL_PROTOCOL)")) + return -1; + + if (!ASSERT_EQ(protocol, IPPROTO_MPTCP, "protocol isn't MPTCP")) + err++; + + /* Output of nstat: + * + * #kernel + * MPTcpExtMPCapableSYNACKRX 1 0.0 + */ + 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, err = 0; + struct mptcpify *mptcpify_skel; + + mptcpify_skel = mptcpify__open_and_load(); + if (!ASSERT_OK_PTR(mptcpify_skel, "skel_open_load")) + return libbpf_get_error(mptcpify_skel); + + err = mptcpify__attach(mptcpify_skel); + if (!ASSERT_OK(err, "skel_attach")) + 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(server_fd); + + 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); +} + 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..53301ae8a8f7 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/mptcpify.c @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023, SUSE. */ + +#include "vmlinux.h" +#include <bpf/bpf_tracing.h> +#include "bpf_tracing_net.h" + +char _license[] SEC("license") = "GPL"; + +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; +}
On 8/11/23 7:54 PM, Geliang Tang wrote:
+static int verify_mptcpify(int server_fd) +{
- socklen_t optlen;
- char cmd[256];
- int protocol;
- int err = 0;
- optlen = sizeof(protocol);
- if (!ASSERT_OK(getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen),
"getsockopt(SOL_PROTOCOL)"))return -1;- if (!ASSERT_EQ(protocol, IPPROTO_MPTCP, "protocol isn't MPTCP"))
err++;- /* Output of nstat:
** #kernel* MPTcpExtMPCapableSYNACKRX 1 0.0*/- 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");
Is the mp-capable something that the regular mptcp user want to learn from a fd also? Does it have a simpler way like to learn this, eg. getsockopt(fd, SOL_MPTCP, MPTCP_xxx), instead of parsing text output?
- if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
On Mon, Aug 14, 2023 at 11:23:49PM -0700, Martin KaFai Lau wrote:
On 8/11/23 7:54 PM, Geliang Tang wrote:
+static int verify_mptcpify(int server_fd) +{
- socklen_t optlen;
- char cmd[256];
- int protocol;
- int err = 0;
- optlen = sizeof(protocol);
- if (!ASSERT_OK(getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen),
"getsockopt(SOL_PROTOCOL)"))return -1;- if (!ASSERT_EQ(protocol, IPPROTO_MPTCP, "protocol isn't MPTCP"))
err++;- /* Output of nstat:
** #kernel* MPTcpExtMPCapableSYNACKRX 1 0.0*/- 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");Is the mp-capable something that the regular mptcp user want to learn from a fd also? Does it have a simpler way like to learn this, eg. getsockopt(fd, SOL_MPTCP, MPTCP_xxx), instead of parsing text output?
Thanks Martin. Yes, you're right. A better one is using getsockopt (MPTCP_INFO) to get the mptcpi_flags, then test the FALLBACK bit to make sure this MPTCP connection didn't fallback. This is, in other word, this MPTCP connection has been established correctly. Something like this:
+ optlen = sizeof(info); + if (!ASSERT_OK(getsockopt(fd, SOL_MPTCP, MPTCP_INFO, &info, &optlen), + "getsockopt(MPTCP_INFO)")) + return -1; + + if (!ASSERT_FALSE(info.mptcpi_flags & MPTCP_INFO_FLAG_FALLBACK, + "MPTCP fallback")) + err++;
It's necessary to add this further check after the MPTCP protocol check using getsockopt(SOL_PROTOCOL). Since in some cases, the MPTCP protocol check is not enough. Say, if we change TCP protocol into MPTCP using "cgroup/sock_create", the hook of BPF_CGROUP_RUN_PROG_INET_SOCK in inet_create(), this place is too late to change the protocol. Although sk->sk_protocol is set to MPTCP correctly, and the MPTCP protocol check using getsockopt(SOL_PROTOCOL) will pass. This MPTCP connection will fallback to TCP connection. So this further check is needed.
-Geliang
- if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
On 8/15/23 3:08 AM, Geliang Tang wrote:
On Mon, Aug 14, 2023 at 11:23:49PM -0700, Martin KaFai Lau wrote:
On 8/11/23 7:54 PM, Geliang Tang wrote:
+static int verify_mptcpify(int server_fd) +{
- socklen_t optlen;
- char cmd[256];
- int protocol;
- int err = 0;
- optlen = sizeof(protocol);
- if (!ASSERT_OK(getsockopt(server_fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen),
"getsockopt(SOL_PROTOCOL)"))return -1;- if (!ASSERT_EQ(protocol, IPPROTO_MPTCP, "protocol isn't MPTCP"))
err++;- /* Output of nstat:
** #kernel* MPTcpExtMPCapableSYNACKRX 1 0.0*/- 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");Is the mp-capable something that the regular mptcp user want to learn from a fd also? Does it have a simpler way like to learn this, eg. getsockopt(fd, SOL_MPTCP, MPTCP_xxx), instead of parsing text output?
Thanks Martin. Yes, you're right. A better one is using getsockopt (MPTCP_INFO) to get the mptcpi_flags, then test the FALLBACK bit to make sure this MPTCP connection didn't fallback. This is, in other word, this MPTCP connection has been established correctly. Something like this:
optlen = sizeof(info);if (!ASSERT_OK(getsockopt(fd, SOL_MPTCP, MPTCP_INFO, &info, &optlen),"getsockopt(MPTCP_INFO)"))return -1;if (!ASSERT_FALSE(info.mptcpi_flags & MPTCP_INFO_FLAG_FALLBACK,"MPTCP fallback"))err++;It's necessary to add this further check after the MPTCP protocol check using getsockopt(SOL_PROTOCOL). Since in some cases, the MPTCP protocol check is not enough. Say, if we change TCP protocol into MPTCP using "cgroup/sock_create", the hook of BPF_CGROUP_RUN_PROG_INET_SOCK in inet_create(), this place is too late to change the protocol. Although sk->sk_protocol is set to MPTCP correctly, and the MPTCP protocol check using getsockopt(SOL_PROTOCOL) will pass. This MPTCP connection will fallback to TCP connection. So this further check is needed.
If I read it correctly, it sounds like the "ip netns... nstat.... awk...grep..." can be replaced with the getsockopt(MPTCP_INFO)? If that is the case, could you respin one more time to do getsockopt(MPTCP_INFO) instead? I would like the test to avoid parsing text output and have less dependency on external binary/library if possible (On top of 'ip', the above uses nstat, awk, grep...). This will make the bpf CI and other developers' environment tricky to maintain. eg. fwiw, although unrelated to the commands used above, my dev environment suddenly like to give this text output when I run "e"grep: "egrep: warning: egrep is obsolescent; using grep -E"
- if (!ASSERT_OK(system(cmd), "No MPTcpExtMPCapableSYNACKRX found!"))
linux-kselftest-mirror@lists.linaro.org
-
Geliang Tang -
Martin KaFai Lau