From 1630764b02bbcbf0980d8080ea6ee8fd9b2cabf0 Mon Sep 17 00:00:00 2001
From: Tristan Schmelcher <tristan.schmelcher@gmail.com>
Date: Sat, 21 May 2022 20:18:14 -0700
Subject: [PATCH] Fix --mptcp on kernels with mainlined MPTCP. Mainlined MPTCP
 on Linux 5.6+ is enabled with IPPROTO_MPTCP rather than setsockopt.

---
 src/local.c    | 10 +++++++++-
 src/netutils.h |  2 ++
 src/redir.c    | 10 +++++++++-
 src/server.c   | 10 +++++++++-
 src/tunnel.c   | 10 +++++++++-
 5 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/src/local.c b/src/local.c
index 47d634ce..200c7c9b 100644
--- a/src/local.c
+++ b/src/local.c
@@ -1272,7 +1272,13 @@ create_remote(listen_ctx_t *listener,
         remote_addr = addr;
     }
 
-    int remotefd = socket(remote_addr->sa_family, SOCK_STREAM, IPPROTO_TCP);
+    int protocol = IPPROTO_TCP;
+#ifdef IPPROTO_MPTCP
+    if (listener->mptcp > 0) {
+        protocol = IPPROTO_MPTCP;
+    }
+#endif
+    int remotefd = socket(remote_addr->sa_family, SOCK_STREAM, protocol);
 
     if (remotefd == -1) {
         ERROR("socket");
@@ -1285,6 +1291,7 @@ create_remote(listen_ctx_t *listener,
     setsockopt(remotefd, SOL_SOCKET, SO_NOSIGPIPE, &opt, sizeof(opt));
 #endif
 
+#ifndef IPPROTO_MPTCP
     if (listener->mptcp > 1) {
         int err = setsockopt(remotefd, SOL_TCP, listener->mptcp, &opt, sizeof(opt));
         if (err == -1) {
@@ -1303,6 +1310,7 @@ create_remote(listen_ctx_t *listener,
             ERROR("failed to enable multipath TCP");
         }
     }
+#endif
 
     if (tcp_outgoing_sndbuf > 0) {
         setsockopt(remotefd, SOL_SOCKET, SO_SNDBUF, &tcp_outgoing_sndbuf, sizeof(int));
diff --git a/src/netutils.h b/src/netutils.h
index 82724195..53603005 100644
--- a/src/netutils.h
+++ b/src/netutils.h
@@ -60,12 +60,14 @@ typedef struct {
     char *port;
 } ss_addr_t;
 
+#ifndef IPPROTO_MPTCP
 /* MPTCP_ENABLED setsockopt values for kernel 4 & 3, best behaviour to be independant of kernel version is to test from newest to the latest values */
 #ifndef MPTCP_ENABLED
 static const char mptcp_enabled_values[] = { 42, 26, 0 };
 #else
 static const char mptcp_enabled_values[] = { MPTCP_ENABLED, 0 };
 #endif
+#endif
 
 #ifndef UPDATE_INTERVAL
 #define UPDATE_INTERVAL 5
diff --git a/src/redir.c b/src/redir.c
index e60bd487..81606b09 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -770,7 +770,13 @@ accept_cb(EV_P_ ev_io *w, int revents)
     int index                    = rand() % listener->remote_num;
     struct sockaddr *remote_addr = listener->remote_addr[index];
 
-    int remotefd = socket(remote_addr->sa_family, SOCK_STREAM, IPPROTO_TCP);
+    int protocol = IPPROTO_TCP;
+#ifdef IPPROTO_MPTCP
+    if (listener->mptcp > 0) {
+	protocol = IPPROTO_MPTCP;
+    }
+#endif
+    int remotefd = socket(remote_addr->sa_family, SOCK_STREAM, protocol);
     if (remotefd == -1) {
         ERROR("socket");
         return;
@@ -808,6 +814,7 @@ accept_cb(EV_P_ ev_io *w, int revents)
 #endif
     }
 
+#ifndef IPPROTO_MPTCP
     // Enable MPTCP
     if (listener->mptcp > 1) {
         int err = setsockopt(remotefd, SOL_TCP, listener->mptcp, &opt, sizeof(opt));
@@ -827,6 +834,7 @@ accept_cb(EV_P_ ev_io *w, int revents)
             ERROR("failed to enable multipath TCP");
         }
     }
+#endif
 
     if (tcp_outgoing_sndbuf > 0) {
         setsockopt(remotefd, SOL_SOCKET, SO_SNDBUF, &tcp_outgoing_sndbuf, sizeof(int));
diff --git a/src/server.c b/src/server.c
index 073e38b2..bf453332 100644
--- a/src/server.c
+++ b/src/server.c
@@ -594,7 +594,13 @@ create_and_bind(const char *host, const char *port, int mptcp)
     }
 
     for (/*rp = result*/; rp != NULL; rp = rp->ai_next) {
-        listen_sock = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
+        int protocol = rp->ai_protocol;
+#ifdef IPPROTO_MPTCP
+        if (mptcp == 1) {
+            protocol = IPPROTO_MPTCP;
+        }
+#endif
+        listen_sock = socket(rp->ai_family, rp->ai_socktype, protocol);
         if (listen_sock == -1) {
             continue;
         }
@@ -616,6 +622,7 @@ create_and_bind(const char *host, const char *port, int mptcp)
             }
         }
 
+#ifndef IPPROTO_MPTCP
         if (mptcp == 1) {
             int i = 0;
             while ((mptcp = mptcp_enabled_values[i]) > 0) {
@@ -629,6 +636,7 @@ create_and_bind(const char *host, const char *port, int mptcp)
                 ERROR("failed to enable multipath TCP");
             }
         }
+#endif
 
         s = bind(listen_sock, rp->ai_addr, rp->ai_addrlen);
         if (s == 0) {
diff --git a/src/tunnel.c b/src/tunnel.c
index 6641fe62..0b68f500 100644
--- a/src/tunnel.c
+++ b/src/tunnel.c
@@ -736,7 +736,13 @@ accept_cb(EV_P_ ev_io *w, int revents)
     int index                    = rand() % listener->remote_num;
     struct sockaddr *remote_addr = listener->remote_addr[index];
 
-    int remotefd = socket(remote_addr->sa_family, SOCK_STREAM, IPPROTO_TCP);
+    int protocol = IPPROTO_TCP;
+#ifdef IPPROTO_MPTCP
+    if (listener->mptcp > 0) {
+        protocol = IPPROTO_MPTCP;
+    }
+#endif
+    int remotefd = socket(remote_addr->sa_family, SOCK_STREAM, protocol);
     if (remotefd == -1) {
         ERROR("socket");
         return;
@@ -767,6 +773,7 @@ accept_cb(EV_P_ ev_io *w, int revents)
     setsockopt(remotefd, SOL_SOCKET, SO_NOSIGPIPE, &opt, sizeof(opt));
 #endif
 
+#ifndef IPPROTO_MPTCP
     if (listener->mptcp > 1) {
         int err = setsockopt(remotefd, SOL_TCP, listener->mptcp, &opt, sizeof(opt));
         if (err == -1) {
@@ -785,6 +792,7 @@ accept_cb(EV_P_ ev_io *w, int revents)
             ERROR("failed to enable multipath TCP");
         }
     }
+#endif
 
     if (tcp_outgoing_sndbuf > 0) {
         setsockopt(remotefd, SOL_SOCKET, SO_SNDBUF, &tcp_outgoing_sndbuf, sizeof(int));