socket: add MPTCP support

.github/scripts/spellcheck.words

@@ -503,6 +503,7 @@ monospace
 MorphOS
 MPE
 MPL
+MPTCP
 mprintf
 MQTT
 mqtt
@@ -523,6 +524,7 @@ mTLS
 MUA
 multicwd
 multiparts
+multipath
 MultiSSL
 mumbo
 musedev

docs/cmdline-opts/Makefile.inc

@@ -161,6 +161,7 @@ DPAGES = \
   max-redirs.md \
   max-time.md \
   metalink.md \
+  mptcp.md \
   negotiate.md \
   netrc-file.md \
   netrc-optional.md \

docs/cmdline-opts/mptcp.md

@@ -0,0 +1,41 @@
+---
+c: Copyright (C) Dorian Craps, <dorian.craps@student.vinci.be>
+SPDX-License-Identifier: curl
+Long: mptcp
+Added: 8.9.0
+Help: Enable Multipath TCP
+Category: connection
+Multi: boolean
+See-also:
+  - tcp-fastopen
+Example:
+  - --mptcp $URL
+---
+
+# `--mptcp`
+
+Enables the use of Multipath TCP (MPTCP) for connections. MPTCP is an extension
+to the standard TCP that allows multiple TCP streams over different network
+paths between the same source and destination. This can enhance bandwidth and
+improve reliability by using multiple paths simultaneously.
+
+MPTCP is beneficial in networks where multiple paths exist between clients and
+servers, such as mobile networks where a device may switch between WiFi and
+cellular data or in wired networks with multiple Internet Service Providers.
+
+## Usage
+
+To use MPTCP for your connections, add the `--mptcp` option when using `curl'.
+
+## Requirements
+
+This feature is currently only supported on Linux starting from kernel 5.6. Only
+TCP connections are modified, hence this option does not effect HTTP/3 (QUIC)
+connections.
+
+The server you are connecting to must also support MPTCP. If not, the connection
+seamlessly falls back to TCP.
+
+## Availability
+
+The `--mptcp` option is available starting from `curl` version 8.9.0.

docs/options-in-versions

@@ -126,6 +126,7 @@
 --max-redirs                         7.5
 --max-time (-m)                      4.0
 --metalink                           7.27.0
+--mptcp                              8.9.0
 --negotiate                          7.10.6
 --netrc (-n)                         4.6
 --netrc-file                         7.21.5

packages/vms/gnv_link_curl.com

@@ -400,6 +400,7 @@ $       link'ldebug'/exe=[.src]curl.exe/dsf=[.src]curl.dsf -
            [.src]curl-tool_bname.o, [.src]curl-tool_cb_dbg.o, -
            [.src]curl-tool_cb_hdr.o, [.src]curl-tool_cb_prg.o, -
            [.src]curl-tool_cb_rea.o, [.src]curl-tool_cb_see.o, -
+           [.src]curl-tool_cb_soc.o, -
            [.src]curl-tool_cb_wrt.o, [.src]curl-tool_cfgable.o, -
            [.src]curl-tool_convert.o, [.src]curl-tool_dirhie.o, -
            [.src]curl-tool_doswin.o, [.src]curl-tool_easysrc.o, -

src/Makefile.inc

@@ -67,6 +67,7 @@ CURL_CFILES = \
   tool_cb_prg.c \
   tool_cb_rea.c \
   tool_cb_see.c \
+  tool_cb_soc.c \
   tool_cb_wrt.c \
   tool_cfgable.c \
   tool_dirhie.c \
@@ -112,6 +113,7 @@ CURL_HFILES = \
   tool_cb_prg.h \
   tool_cb_rea.h \
   tool_cb_see.h \
+  tool_cb_soc.h \
   tool_cb_wrt.h \
   tool_cfgable.h \
   tool_dirhie.h \

src/tool_cb_soc.c

@@ -0,0 +1,58 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "tool_setup.h"
+
+#ifdef HAVE_NETINET_IN_H
+#include <netinet/in.h> /* IPPROTO_TCP */
+#endif
+
+#include "tool_cb_soc.h"
+
+/*
+** callback for CURLOPT_OPENSOCKETFUNCTION
+**
+** Notice that only Linux is supported for the moment.
+*/
+
+curl_socket_t tool_socket_open_mptcp_cb(void *clientp,
+                                        curlsocktype purpose,
+                                        struct curl_sockaddr *addr)
+{
+  int protocol = addr->protocol;
+
+  (void)clientp;
+  (void)purpose;
+
+  if(protocol == IPPROTO_TCP)
+#if defined(__linux__)
+#  ifndef IPPROTO_MPTCP
+#  define IPPROTO_MPTCP 262
+#  endif
+    protocol = IPPROTO_MPTCP;
+#else
+    return CURL_SOCKET_BAD;
+#endif
+
+  return socket(addr->family, addr->socktype, protocol);
+}

src/tool_cb_soc.h

@@ -0,0 +1,36 @@
+#ifndef HEADER_CURL_TOOL_CB_SOC_H
+#define HEADER_CURL_TOOL_CB_SOC_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+#include "tool_setup.h"
+
+/*
+** callback for CURLOPT_OPENSOCKETFUNCTION
+*/
+
+curl_socket_t tool_socket_open_mptcp_cb(void *clientp,
+                                        curlsocktype purpose,
+                                        struct curl_sockaddr *addr);
+
+#endif /* HEADER_CURL_TOOL_CB_SOC_H */

src/tool_cfgable.h

@@ -292,6 +292,7 @@ struct OperationConfig {
     CLOBBER_NEVER, /* If the file exists, always fail */
     CLOBBER_ALWAYS /* If the file exists, always overwrite it */
   } file_clobber_mode;
+  bool mptcp;                     /* enable MPTCP support */
   struct GlobalConfig *global;
   struct OperationConfig *prev;
   struct OperationConfig *next;   /* Always last in the struct */

src/tool_getparam.c

@@ -200,6 +200,7 @@ typedef enum {
   C_MAX_REDIRS,
   C_MAX_TIME,
   C_METALINK,
+  C_MPTCP,
   C_NEGOTIATE,
   C_NETRC,
   C_NETRC_FILE,
@@ -482,6 +483,7 @@ static const struct LongShort aliases[]= {
   {"max-redirs",                 ARG_STRG, ' ', C_MAX_REDIRS},
   {"max-time",                   ARG_STRG, 'm', C_MAX_TIME},
   {"metalink",                   ARG_BOOL, ' ', C_METALINK},
+  {"mptcp",                      ARG_BOOL, ' ', C_MPTCP},
   {"negotiate",                  ARG_BOOL, ' ', C_NEGOTIATE},
   {"netrc",                      ARG_BOOL, 'n', C_NETRC},
   {"netrc-file",                 ARG_FILE, ' ', C_NETRC_FILE},
@@ -2793,6 +2795,9 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
         }
       }
       break;
+    case C_MPTCP: /* --mptcp */
+      config->mptcp = TRUE;
+      break;
     default: /* unknown flag */
       err = PARAM_OPTION_UNKNOWN;
       break;

src/tool_listhelp.c

@@ -381,6 +381,9 @@ const struct helptxt helptext[] = {
   {"    --metalink",
    "Process given URLs as metalink XML file",
    CURLHELP_MISC},
+  {"    --mptcp",
+   "Enable Multipath TCP",
+   CURLHELP_CONNECTION},
   {"    --negotiate",
    "Use HTTP Negotiate (SPNEGO) authentication",
    CURLHELP_AUTH | CURLHELP_HTTP},

src/tool_operate.c

@@ -56,6 +56,7 @@
 #include "tool_cb_prg.h"
 #include "tool_cb_rea.h"
 #include "tool_cb_see.h"
+#include "tool_cb_soc.h"
 #include "tool_cb_wrt.h"
 #include "tool_dirhie.h"
 #include "tool_doswin.h"
@@ -1289,6 +1290,10 @@ static CURLcode single_transfer(struct GlobalConfig *global,
         if(config->tcp_fastopen)
           my_setopt(curl, CURLOPT_TCP_FASTOPEN, 1L);
 
+        if(config->mptcp)
+          my_setopt(curl, CURLOPT_OPENSOCKETFUNCTION,
+                    tool_socket_open_mptcp_cb);
+
         /* where to store */
         my_setopt(curl, CURLOPT_WRITEDATA, per);
         my_setopt(curl, CURLOPT_INTERLEAVEDATA, per);