First version of Multipath TCP support in curl by obonaventure · Pull Request #9713 · curl/curl

obonaventure · 2022-10-12T21:06:23Z

Initial support for Multipath TCP for curl. Multipath TCP is a TCP extension defined in RFC8684 that is supported by recent Linux kernels (5.13+). Multipath TCP allows a TCP connection to use different paths (e.g. Wi-Fi and cellular on smartphones, IPv4 and IPv6, ...). Multipath TCP is enabled by default on recent Linux distributions (Debian, Ubuntu, Redhat,...)

This patch provides the --multipath command line option that enables Multipath TCP when set. If running on a kernel that does not support Multipath TCP, curl remembers the fact that Multipath TCP does not work and does not attempt anymore to use Multipath TCP when creating a TCP connection. Another possibility would be to always enable Multipath TCP by default on Linux.

With the patch, curl reports the activation of Multipath TCP when interacting with a Multipath TCP server.

Compile with -DMPTCP to enable Multipath TCP support

* Multipath TCP is enabled.
*   Trying [2001:41d0:a:ffcf::1]:80...
* Failed to set TCP_KEEPIDLE on fd 5
* Failed to set TCP_KEEPINTVL on fd 5
* Connected to test.multipath-tcp.org (2001:41d0:a:ffcf::1) port 80 (#0)
* Multipath TCP was accepted by the remote server.
> GET / HTTP/1.1
> Host: test.multipath-tcp.org
> User-Agent: curl/7.86.0-DEV
> Accept: */*
>
* Mark bundle as not supporting multiuse < HTTP/1.1 200 OK
< Content-Type: text/html
< Accept-Ranges: bytes
< ETag: "4215149735"
< Last-Modified: Tue, 05 Jul 2022 16:11:47 GMT
< Content-Length: 389
< Date: Wed, 12 Oct 2022 16:32:51 GMT
< Server: lighttpd/1.4.59
<
<!DOCTYPE html>
<html>
<head>
<title>Welcome to test.multipath-tcp.org!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to test.multipath-tcp.org !</h1>
<p>This web server runs Multipath TCP v1</p>

<p><em>Thank you for using Multipath TCP.</em></p> </body>
</html>
* Connection #0 to host test.multipath-tcp.org left intact

First version of Multipath TCP support in curl, compile with ./configure CPPFLAGS="-DMPTCP"

Initial support for Multipath TCP for curl. Multipath TCP is a TCP extension defined in RFC8684 that is supported by recent Linux kernels (5.13+). Multipath TCP allows a TCP connection to use different paths (e.g. Wi-Fi and cellular on smartphones, IPv4 and IPv6, ...). Multipath TCP is enabled by default on recent Linux distributions (Debian, Ubuntu, Redhat,...) This patch provides the --multipath command line option that enables Multipath TCP when set. If running on a kernel that does not support Multipath TCP, curl remembers the fact that Multipath TCP does not work and does not attempt anymore to use Multipath TCP when creating a TCP connection. Another possibility would be to always enable Multipath TCP by default on Linux. With the patch, curl reports the activation of Multipath TCP when interacting with a Multipath TCP server. Compile with -DMPTCP to enable Multipath TCP support * Multipath TCP is enabled. * Trying [2001:41d0:a:ffcf::1]:80... * Failed to set TCP_KEEPIDLE on fd 5 * Failed to set TCP_KEEPINTVL on fd 5 * Connected to test.multipath-tcp.org (2001:41d0:a:ffcf::1) port 80 (#0) * Multipath TCP was accepted by the remote server. > GET / HTTP/1.1 > Host: test.multipath-tcp.org > User-Agent: curl/7.86.0-DEV > Accept: */* > * Mark bundle as not supporting multiuse < HTTP/1.1 200 OK < Content-Type: text/html < Accept-Ranges: bytes < ETag: "4215149735" < Last-Modified: Tue, 05 Jul 2022 16:11:47 GMT < Content-Length: 389 < Date: Wed, 12 Oct 2022 16:32:51 GMT < Server: lighttpd/1.4.59 < <!DOCTYPE html> <html> <head> <title>Welcome to test.multipath-tcp.org!</title> <style> body { width: 35em; margin: 0 auto; font-family: Tahoma, Verdana, Arial, sans-serif; } </style> </head> <body> <h1>Welcome to test.multipath-tcp.org !</h1> <p>This web server runs Multipath TCP v1</p> <p><em>Thank you for using Multipath TCP.</em></p> </body> </html> * Connection #0 to host test.multipath-tcp.org left intact First version of Multipath TCP support in curl, compile with ./configure CPPFLAGS="-DMPTCP"

bagder

Thanks for your contribution. I think this is a future that might get appreciated. I think the PR needs a little more polish though. There is also no docs. I imagine creating tests for this is hard.

bagder · 2022-10-12T21:15:29Z

include/curl/curl.h

+  /* Set Multipath TCP */
+  CURLOPT(CURLOPT_TCP_MULTIPATH, CURLOPTTYPE_LONG, 316),
+#endif
+


This is a public header, it cannot use #ifdefs like this. The symbols need to be provided no matter what.

bagder · 2022-10-12T21:17:23Z

lib/connect.c

+#endif /* MPTCP */
+
+
+


This block looks like it's there for debugging? Maybe use #ifdef DEBUGBUILD as well?

Yes, good suggestion

bagder · 2022-10-12T21:18:19Z

lib/connect.c

    Curl_set_in_callback(data, false);
  }
-  else
+  else 


Please don't modify whitespace.

bagder · 2022-10-12T21:18:27Z

lib/connect.c

 #endif

  return CURLE_OK;
+


bagder · 2022-10-12T21:18:36Z

lib/connect.c

    conn->bits.close = closeit; /* the only place in the source code that
                                   should assign this bit */
  }
+


bagder · 2022-10-12T21:20:19Z

lib/socketpair.c

 #include <netinet/in.h> /* IPPROTO_TCP */
 #endif
+
+


bagder · 2022-10-12T21:20:32Z

lib/socketpair.c

  (void)protocol;
-
-  listener = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+  printf("mptcp\n");


debug leftover?

bagder · 2022-10-12T21:20:40Z

lib/socketpair.c

-
-  listener = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+  printf("mptcp\n");
+  listener = socket(AF_INET, SOCK_STREAM, IPPROTO_MPTCP);


bagder · 2022-10-12T21:21:11Z

lib/socketpair.h

+#endif
+#endif
+
+


Why duplicate this snippet?

This is mistake, apologies. Windows does not support MPTCP and nothing needs to be changed in this file

bagder · 2022-10-12T21:22:48Z

src/tool_getparam.c

  {"Em", "tlsauthtype",              ARG_STRING},
+#ifdef MPTCP
+  {"EM", "multipath",                ARG_BOOL},
+#endif  


The cmdline options cannot be ifdef'ed like this, as the tool might not know what features the lib was built with.

obonaventure · 2022-10-13T08:02:44Z

Thanks for your comments, I'm looking at them and will propose an update. I'll propose some documentation. For the tests, I can propose a modification to the http server to enable multipath tcp and then add a few tests. These tests would only work on recent linux kernels.

bagder · 2022-12-03T11:24:15Z

Additionally: macOS supports multipath TCP as well so it would make sense to provide this feature there was well.

Are you still up for working on this PR?

bagder · 2023-05-14T21:28:52Z

Abandoned.

gvanem · 2023-05-15T07:47:01Z

Looks like someone else has added MTCP to curl (on Windows at least):
https://github.com/ngi-mptcp/curl/wiki/Multipath-TCP-on-Windows-10

With the help of wintap and LKL; a Linux Kernel Library. Fascinating stuff.

bagder added the connecting & proxies label Oct 12, 2022

bagder reviewed Oct 12, 2022

View reviewed changes

bagder added the feature-window A merge of this requires an open feature window label Oct 13, 2022

bagder closed this May 14, 2023

This was referenced Apr 4, 2024

functional option MPTCP with --mptcp CrapsDorian/curl#2

Closed

socket: add MPTCP support #13278

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obonaventure commented Oct 12, 2022 • edited by vszakats Loading Uh oh! There was an error while loading. Please reload this page.

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obonaventure commented Oct 13, 2022

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bagder commented Dec 3, 2022

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bagder commented May 14, 2023

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gvanem commented May 15, 2023

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obonaventure commented Oct 12, 2022 •

edited by vszakats

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