Fetch a working url for mininet setup

Github does not allow git:// link anymore. This was fixed by commit
c3ba039a but there is no new release of mininet. Thus, we need to use
the script of this commit.

ipmininet/install/install.py

@@ -12,6 +12,10 @@
 LibyangVersion = "v1.0.215"
 ExaBGPVersion = "4.2.11"
 
+# XXX: We need the explicit script until the following issue is fixed:
+#      https://github.com/mininet/mininet/issues/1120
+MininetInstallCommit = "c3ba039a9781c6c5f475b7c88ff577185747a1da"
+
 os.environ["PATH"] = "%s:/sbin:/usr/sbin/:/usr/local/sbin" % os.environ["PATH"]
 
 
@@ -65,10 +69,18 @@ def install_mininet(output_dir: str, pip_install=True):
         mininet_opts = "-a"
 
     sh("git clone https://github.com/mininet/mininet.git", cwd=output_dir)
+    # Save valid version of mininet install script
+    sh("git checkout %s" % MininetInstallCommit,
+       cwd=os.path.join(output_dir, "mininet/util"))
+    sh("cp install.sh install.tmp.sh",
+       cwd=os.path.join(output_dir, "mininet/util"))
+    # Use it in the fixed version of Mininet
     sh("git checkout %s" % MininetVersion,
-       cwd=os.path.join(output_dir, "mininet"))
-    sh("mininet/util/install.sh %s -s ." % mininet_opts,
-       cwd=output_dir)
+       cwd=os.path.join(output_dir, "mininet/util"))
+    sh("mv install.tmp.sh install.sh",
+       cwd=os.path.join(output_dir, "mininet/util"))
+    sh("./install.sh %s -s ." % mininet_opts,
+       cwd=os.path.join(output_dir, "mininet/util"))
 
     if pip_install:
         dist.pip_install("mininet/", cwd=output_dir)