MPTCP support #1
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Multipath TCP (MPTCP), standardized in RFC8684 [1], is a TCP extension that enables a TCP connection to use different paths. Multipath TCP has been used for several use cases. On smartphones, MPTCP enables seamless handovers between cellular and Wi-Fi networks while preserving established connections. This use-case is what pushed Apple to use MPTCP since 2013 in multiple applications [2]. On dual-stack hosts, Multipath TCP enables the TCP connection to automatically use the best performing path, either IPv4 or IPv6. If one path fails, MPTCP automatically uses the other path. To benefit from MPTCP, both the client and the server have to support it. Multipath TCP is a backward-compatible TCP extension that is enabled by default on recent Linux distributions (Debian, Ubuntu, Redhat, ...). Multipath TCP is included in the Linux kernel since version 5.6 [3]. To use it on Linux, an application must explicitly enable it when creating the socket. No need to change anything else in the application. This attached patch adds the "mptcp" global option in the config, which allows the creation of an MPTCP socket instead of TCP on Linux. If Multipath TCP is not supported on the system, an error will be reported, and the application will stop. A test has been added, it is a copy of "default_rules.vtc" in tcp-rules with the addition of "mptcp" in the config. I'm not sure what else needs to be tested for the moment, with this global MPTCP option. Note: another patch is coming to support enabling MPTCP per address, but I prefer to already send this patch, just in case, as I will soon have less time to dedicate to this. Due to the limited impact within a data center environment, we have decided not to implement MPTCP between the proxy and the servers. The high-speed, low-latency nature of data center networks reduces the benefits of MPTCP, making the complexity of its implementation unnecessary in this context. Developed with the help of Matthieu Baerts (matttbe@kernel.org) and Olivier Bonaventure (Olivier.Bonaventure@uclouvain.be) Link: https://www.rfc-editor.org/rfc/rfc8684.html [1] Link: https://www.tessares.net/apples-mptcp-story-so-far/ [2] Link: https://www.mptcp.dev [3] Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
To be used with:
mptcp{,4,6}@<address>[:port1[-port2]]
MPTCP v4 and v6 protocols have been added: they are mainly a copy of the
TCP ones, with small differences: names, proto, and receivers lists.
These protocols are stored in __protocol_by_family, as an alternative to
TCP, similar to what has been done with QUIC. By doing that, the size of
__protocol_by_family has not been increased, and it behaves like TCP.
Co-developed-by: Dorian Craps <dorian.craps@student.vinci.be>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
matttbe
pushed a commit
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Jun 3, 2024
At least 3.9.0 version of libressl TLS stack does not behave as others stacks like quictls which
make SSL_do_handshake() return an error when no cipher could be negotiated
in addition to emit a TLS alert(0x28). This is the case when TLS_AES_128_CCM_SHA256
is forced as TLS1.3 cipher from the client side. This make haproxy enter a code
path which leads to a crash as follows:
[Switching to Thread 0x7ffff76b9640 (LWP 23902)]
0x0000000000487627 in quic_tls_key_update (qc=qc@entry=0x7ffff00371f0) at src/quic_tls.c:910
910 struct quic_kp_trace kp_trace = {
(gdb) list
905 {
906 struct quic_tls_ctx *tls_ctx = &qc->ael->tls_ctx;
907 struct quic_tls_secrets *rx = &tls_ctx->rx;
908 struct quic_tls_secrets *tx = &tls_ctx->tx;
909 /* Used only for the traces */
910 struct quic_kp_trace kp_trace = {
911 .rx_sec = rx->secret,
912 .rx_seclen = rx->secretlen,
913 .tx_sec = tx->secret,
914 .tx_seclen = tx->secretlen,
(gdb) p qc
$1 = (struct quic_conn *) 0x7ffff00371f0
(gdb) p qc->ael
$2 = (struct quic_enc_level *) 0x0
(gdb) bt
#0 0x0000000000487627 in quic_tls_key_update (qc=qc@entry=0x7ffff00371f0) at src/quic_tls.c:910
#1 0x000000000049bca9 in qc_ssl_provide_quic_data (len=268, data=<optimized out>, ctx=0x7ffff0047f80, level=<optimized out>, ncbuf=<optimized out>) at src/quic_ssl.c:617
#2 qc_ssl_provide_all_quic_data (qc=qc@entry=0x7ffff00371f0, ctx=0x7ffff0047f80) at src/quic_ssl.c:688
haproxy#3 0x00000000004683a7 in quic_conn_io_cb (t=0x7ffff0047f30, context=0x7ffff00371f0, state=<optimized out>) at src/quic_conn.c:760
haproxy#4 0x000000000063cd9c in run_tasks_from_lists (budgets=budgets@entry=0x7ffff76961f0) at src/task.c:596
haproxy#5 0x000000000063d934 in process_runnable_tasks () at src/task.c:876
haproxy#6 0x0000000000600508 in run_poll_loop () at src/haproxy.c:3073
haproxy#7 0x0000000000600b67 in run_thread_poll_loop (data=<optimized out>) at src/haproxy.c:3287
haproxy#8 0x00007ffff7f6ae45 in start_thread () from /lib64/libpthread.so.0
haproxy#9 0x00007ffff78254af in clone () from /lib64/libc.so.6
When a TLS alert is emitted, haproxy calls quic_set_connection_close() which sets
QUIC_FL_CONN_IMMEDIATE_CLOSE connection flag. This is this flag which is tested
by this patch to make the handshake fail even if SSL_do_handshake() does not
return an error. This test is specific to libressl and never run with
others TLS stack.
Thank you to @lgv5 and @botovq for having reported this issue in GH haproxy#2569.
Must be backported as far as 2.6.
matttbe
pushed a commit
that referenced
this pull request
Jun 3, 2024
In ssl_sock_load_ocsp() it is better to initialize local scope variable
'callback' function pointer as NULL, while we are declaring it. According to
SSL_CTX_get_tlsext_status_cb() API, then we will provide a pointer to this
'on stack' variable in order to check, if the callback was already set before:
OpenSSL 1.x.x and 3.x.x:
long SSL_CTX_get_tlsext_status_cb(SSL_CTX *ctx, int (**callback)(SSL *, void *));
long SSL_CTX_set_tlsext_status_cb(SSL_CTX *ctx, int (*callback)(SSL *, void *));
WolfSSL 5.7.0:
typedef int(*tlsextStatusCb)(WOLFSSL* ssl, void*);
WOLFSSL_API int wolfSSL_CTX_get_tlsext_status_cb(WOLFSSL_CTX* ctx, tlsextStatusCb* cb);
WOLFSSL_API int wolfSSL_CTX_set_tlsext_status_cb(WOLFSSL_CTX* ctx, tlsextStatusCb cb);
When this func ptr variable stays uninitialized, haproxy comipled with ASAN
crushes in ssl_sock_load_ocsp():
./haproxy -d -f haproxy.cfg
...
AddressSanitizer:DEADLYSIGNAL
=================================================================
==114919==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x5eab8951bb32 bp 0x7ffcdd6d8410 sp 0x7ffcdd6d82e0 T0)
==114919==The signal is caused by a READ memory access.
==114919==Hint: address points to the zero page.
#0 0x5eab8951bb32 in ssl_sock_load_ocsp /home/vk/projects/haproxy/src/ssl_sock.c:1248:22
#1 0x5eab89510d65 in ssl_sock_put_ckch_into_ctx /home/vk/projects/haproxy/src/ssl_sock.c:3389:6
...
This happens, because callback variable is allocated on the stack. As not
being explicitly initialized, it may contain some garbage value at runtime,
due to the linked crypto library update or recompilation.
So, following ssl_sock_load_ocsp code, SSL_CTX_get_tlsext_status_cb() may
fail, callback will still contain its initial garbage value,
'if (!callback) {...' test will put us on the wrong path to access some
ocsp_cbk_arg properties via its pointer, which won't be set and like this
we will finish with segmentation fault.
Must be backported in all stable versions. All versions does not have
the ifdef, the previous cleanup patch is useful starting from the 2.7
version.
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just to track modifications