functional option MPTCP with --multipath-tcp

docs/cmdline-opts/Makefile.inc

@@ -160,6 +160,7 @@ 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 +1,32 @@
+---
+c: Copyright (C) Dorian Craps, <dorian.craps@student.vinci.be>
+SPDX-License-Identifier: curl
+Long: mptcp
+Added: X.XX.XX (Version you added MPTCP)
+Help: Enable Multipath TCP (MPTCP)
+Category: connection
+Multi: boolean
+See-also:
+  - http2
+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 Wi-Fi and cellular data or in wired networks with multiple ISPs.
+
+## Usage
+
+To use MPTCP for your connections, add the `--mptcp` option when using `curl`:
+
+## Requirements
+
+- Your operating system must support MPTCP, and it must be enabled.
+- The server you are connecting to must also support MPTCP.
+
+## Availability
+
+The `--mptcp` option is available starting from `curl` version X.XX.XX.

include/curl/curl.h

@@ -2206,6 +2206,9 @@ typedef enum {
   /* millisecond version */
   CURLOPT(CURLOPT_SERVER_RESPONSE_TIMEOUT_MS, CURLOPTTYPE_LONG, 324),
 
+  /* Set MPTCP */
+  CURLOPT(CURLOPT_MPTCP, CURLOPTTYPE_LONG, 325),
+
   CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;
 

lib/cf-socket.c

@@ -244,6 +244,10 @@ void Curl_sock_assign_addr(struct Curl_sockaddr_ex *dest,
     dest->socktype = SOCK_STREAM;
     dest->protocol = IPPROTO_IP;
     break;
+  case TRNSPRT_MPTCP:
+    dest->socktype = SOCK_STREAM;
+    dest->protocol = IPPROTO_MPTCP;
+    break;
   default: /* UDP and QUIC */
     dest->socktype = SOCK_DGRAM;
     dest->protocol = IPPROTO_UDP;
@@ -1609,7 +1613,12 @@ CURLcode Curl_cf_tcp_create(struct Curl_cfilter **pcf,
   if(!ctx) {
     result = CURLE_OUT_OF_MEMORY;
     goto out;
+  }  
+#ifdef __linux__
+  if (data->set.mptcp)  {
+     transport = TRNSPRT_MPTCP;
   }
+#endif
   cf_socket_ctx_init(ctx, ai, transport);
 
   result = Curl_cf_create(&cf, &Curl_cft_tcp, ctx);

lib/cf-socket.h

@@ -28,6 +28,10 @@
 #include "nonblock.h" /* for curlx_nonblock(), formerly Curl_nonblock() */
 #include "sockaddr.h"
 
+#ifndef IPPROTO_MPTCP
+#define IPPROTO_MPTCP 262
+#endif
+
 struct Curl_addrinfo;
 struct Curl_cfilter;
 struct Curl_easy;

lib/setopt.c

@@ -2932,6 +2932,9 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option, va_list param)
     result = CURLE_NOT_BUILT_IN;
 #endif
     break;
+  case  CURLOPT_MPTCP:
+    data->set.mptcp = TRUE;
+    break;  
   case CURLOPT_SSL_ENABLE_NPN:
     break;
   case CURLOPT_SSL_ENABLE_ALPN:

lib/urldata.h

@@ -894,6 +894,7 @@ struct ldapconninfo;
 #define TRNSPRT_UDP 4
 #define TRNSPRT_QUIC 5
 #define TRNSPRT_UNIX 6
+#define TRNSPRT_MPTCP 7
 
 /*
  * The connectdata struct contains all fields and variables that should be
@@ -1941,6 +1942,7 @@ struct UserDefined {
 #ifdef USE_WEBSOCKETS
   BIT(ws_raw_mode);
 #endif
+  bool mptcp; /* enable MPTCP support */
 };
 
 struct Names {

src/tool_cfgable.c

@@ -45,6 +45,7 @@ void config_init(struct OperationConfig *config)
   config->http09_allowed = FALSE;
   config->ftp_skip_ip = TRUE;
   config->file_clobber_mode = CLOBBER_DEFAULT;
+  config->mptcp = FALSE;
   curlx_dyn_init(&config->postdata, MAX_FILE2MEMORY);
 }
 

src/tool_cfgable.h

@@ -298,6 +298,7 @@ struct OperationConfig {
   struct State state;             /* for create_transfer() */
   bool rm_partial;                /* on error, remove partially written output
                                      files */
+  bool mptcp;
 };
 
 struct GlobalConfig {

src/tool_getparam.c

@@ -199,6 +199,7 @@ typedef enum {
   C_MAX_REDIRS,
   C_MAX_TIME,
   C_METALINK,
+  C_MPTCP,
   C_NEGOTIATE,
   C_NETRC,
   C_NETRC_FILE,
@@ -480,6 +481,7 @@ 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},
@@ -2739,6 +2741,9 @@ 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_operate.c

@@ -1291,6 +1291,9 @@ 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_MPTCP, 1L);        
+
         /* where to store */
         my_setopt(curl, CURLOPT_WRITEDATA, per);
         my_setopt(curl, CURLOPT_INTERLEAVEDATA, per);