Try value 42 for mptcp (fallback to 26)

src/main.c

@@ -53,8 +53,6 @@
 #define GT_ABYTES    (16)
 #define GT_KEYBYTES  (32)
 
-#define MPTCP_ENABLED (26)
-
 static struct {
     volatile sig_atomic_t quit;
     volatile sig_atomic_t info;
@@ -116,13 +114,16 @@ enum sk_opt {
     sk_acceptfilter,
     sk_quickack,
     sk_user_timeout,
-    sk_mptcp,
+    sk_mptcp_26,
+    sk_mptcp_42,
 };
 
-static void sk_set (int fd, enum sk_opt opt, const void *val, socklen_t len)
+static int sk_set (int fd, enum sk_opt opt, const void *val, socklen_t len)
 {
-    if (!val || len<=0)
-        return;
+    if (!val || len<=0) {
+        errno = EINVAL;
+        return -1;
+    }
 
     struct {
         const char *name;
@@ -173,33 +174,44 @@ static void sk_set (int fd, enum sk_opt opt, const void *val, socklen_t len)
             1, IPPROTO_TCP, TCP_USER_TIMEOUT,
 #endif
         },
-        [sk_mptcp] = { "MPTCP_ENABLED",
-#ifdef MPTCP_ENABLED
-            1, IPPROTO_TCP, MPTCP_ENABLED,
-#endif
-        },
+        [sk_mptcp_26] = { "MPTCP_ENABLED (26)", 1, IPPROTO_TCP, 26 },
+        [sk_mptcp_42] = { "MPTCP_ENABLED (42)", 1, IPPROTO_TCP, 42 },
     };
 
     if (!opts[opt].present) {
         gt_na(opts[opt].name);
-        return;
+        errno = EINVAL;
+        return -1;
     }
 
-    if (setsockopt(fd, opts[opt].level, opts[opt].option, val, len)==-1)
+    int ret = setsockopt(fd, opts[opt].level, opts[opt].option, val, len);
+
+    if (ret==-1) {
+        int err = errno;
         gt_log("couldn't set socket option `%s'\n", opts[opt].name);
+        errno = err;
+    }
+
+    return ret;
 }
 
-static void sk_set_int (int fd, enum sk_opt opt, int val)
+static int sk_set_int (int fd, enum sk_opt opt, int val)
 {
     return sk_set(fd, opt, &val, sizeof(val));
 }
 
+static void sk_set_mptcp (int fd)
+{
+    if (sk_set_int(fd, sk_mptcp_42, 1)==-1)
+        sk_set_int(fd, sk_mptcp_26, 1);
+}
+
 static int sk_listen (int fd, struct addrinfo *ai)
 {
     sk_set_int(fd, sk_reuseaddr, 1);
 
     if (gt.mptcp)
-        sk_set_int(fd, sk_mptcp, 1);
+        sk_set_mptcp(fd);
 
     if (bind(fd, ai->ai_addr, ai->ai_addrlen)==-1) {
         perror("bind");
@@ -226,7 +238,7 @@ static int sk_connect (int fd, struct addrinfo *ai)
     fd_set_nonblock(fd);
 
     if (gt.mptcp)
-        sk_set_int(fd, sk_mptcp, 1);
+        sk_set_mptcp(fd);
 
     int ret = connect(fd, ai->ai_addr, ai->ai_addrlen);