test: netns: Generalize IsolatedMacVlan to support multiple interfaces

This is needed to create namespaces with MACVLANs from different
parent interfaces. The first consumer will be a Two-Port Mac
Relay (TPMR), so that we can control the flow of packets between two
nodes.

test/infamy/netns.py

@@ -18,31 +18,53 @@ def setns(fd, nstype):
     __NR_setns = 308
     __libc.syscall(__NR_setns, fd, nstype)
 
-class IsolatedMacVlan:
-    """Create an isolated interface on top of a PC interface."""
-    def __init__(self, parent, ifname="iface", lo=True):
+class IsolatedMacVlans:
+    """A network namespace containing a multiple MACVLANs
+
+    Stacks a MACVLAN on top of each specificed controller interface,
+    and moves those interfaces to a separate namespace, isolating it
+    from all others.
+
+    NOTE: For the simple case when only one interface needs to be
+    mapped, see IsolatedMacVlan below.
+
+    Example:
+
+    netns = IsolatedMacVlans({ "eth2": "a", "eth3": "b" })
+
+             netns:
+             .--------.
+             | a    b | (MACVLANs)
+             '-+----+-'
+               |    |
+    eth0 eth1 eth2 eth3
+
+    """
+
+    def __init__(self, ifmap, lo=True):
         self.sleeper = None
-        self.parent, self.ifname, self.lo = parent, ifname, lo
+        self.ifmap, self.lo = ifmap, lo
         self.ping_timeout = env.ENV.attr("ping_timeout", 5)
 
-    def __enter__(self):
+    def start(self):
         self.sleeper = subprocess.Popen(["unshare", "-r", "-n", "sh", "-c",
                                          "echo && exec sleep infinity"],
                                         stdout=subprocess.PIPE)
         self.sleeper.stdout.readline()
 
         try:
-            subprocess.run(["ip", "link", "add",
-                            "dev", self.ifname,
-                            "link", self.parent,
-                            "address", self._stable_mac(),
-                            "netns", str(self.sleeper.pid),
-                            "type", "macvlan"], check=True)
-            self.runsh(f"""
-            while ! ip link show dev {self.ifname}; do
-                sleep 0.1
-            done
-            """)
+            for parent, ifname in self.ifmap.items():
+                subprocess.run(["ip", "link", "add",
+                                "dev", ifname,
+                                "link", parent,
+                                "address", self._stable_mac(parent),
+                                "netns", str(self.sleeper.pid),
+                                "type", "macvlan"], check=True)
+                self.runsh(f"""
+                while ! ip link show dev {ifname}; do
+                    sleep 0.1
+                done
+                """)
         except Exception as e:
             self.__exit__(None, None, None)
             raise e
@@ -56,12 +78,18 @@ class IsolatedMacVlan:
 
         return self
 
-    def __exit__(self, val, typ, tb):
+    def stop(self):
         self.sleeper.kill()
         self.sleeper.wait()
         time.sleep(0.5)
 
-    def _stable_mac(self):
+    def __enter__(self):
+        return self.start()
+
+    def __exit__(self, val, typ, tb):
+        return self.stop()
+
+    def _stable_mac(self, parent):
         """Generate address for MACVLAN
 
         By default, the kernel will assign a random address. This
@@ -75,7 +103,7 @@ class IsolatedMacVlan:
         the resource exhaustion issue.
 
         """
-        random.seed(self.parent)
+        random.seed(parent)
         a = list(random.randbytes(6))
         a[0] |= 0x02
         a[0] &= ~0x01
@@ -146,13 +174,13 @@ class IsolatedMacVlan:
             ip -{p} route add {subnet}{prefix_length} via {nexthop}
             """, check=True)
 
-    def addip(self, addr, prefix_length=24, proto="ipv4"):
+    def addip(self, ifname, addr, prefix_length=24, proto="ipv4"):
         p=proto[3]
 
         self.runsh(f"""
             set -ex
             ip link set iface up
-            ip -{p} addr add {addr}/{prefix_length} dev iface
+            ip -{p} addr add {addr}/{prefix_length} dev {ifname}
             """, check=True)
 
 
@@ -188,8 +216,7 @@ class IsolatedMacVlan:
 
         raise Exception(res)
 
-    def must_receive(self, expr, timeout=None, ifname=None, must=True):
-        ifname = ifname if ifname else self.ifname
+    def must_receive(self, expr, ifname, timeout=None, must=True):
         timeout = timeout if timeout else self.ping_timeout
 
         tshark = self.run(["tshark", "-nl", f"-i{ifname}",
@@ -207,10 +234,43 @@ class IsolatedMacVlan:
     def must_not_receive(self, *args, **kwargs):
         self.must_receive(*args, **kwargs, must=False)
 
-    def pcap(self, expr, ifname=None):
-        ifname = ifname if ifname else self.ifname
+    def pcap(self, expr, ifname):
         return Pcap(self, ifname, expr)
 
+class IsolatedMacVlan(IsolatedMacVlans):
+    """A network namespace containing a single MACVLAN
+
+    Stacks a MACVLAN on top of an interface on the controller, and
+    moves that interface to a separate namespace, isolating it from
+    all other interfaces.
+
+    Example:
+
+    netns = IsolatedMacVlan("eth3")
+
+                netns:
+                .-------.
+                | iface | (MACVLAN)
+                '---+---'
+                    |
+    eth0 eth1 eth2 eth3
+
+    """
+    def __init__(self, parent, ifname="iface", lo=True):
+        self._ifname = ifname
+        return super().__init__(ifmap={ parent: ifname }, lo=lo)
+
+    def addip(self, addr, prefix_length=24, proto="ipv4"):
+        return super().addip(ifname=self._ifname, addr=addr, prefix_length=prefix_length, proto=proto)
+
+    def must_receive(self, expr, timeout=None, ifname=None, must=True):
+        ifname = ifname if ifname else self._ifname
+        return super().must_receive(expr=expr, ifname=ifname, timeout=timeout, must=must)
+
+    def pcap(self, expr, ifname=None):
+        ifname = ifname if ifname else self._ifname
+        return super().pcap(expr=expr, ifname=ifname)
+
 class Pcap:
     def __init__(self, netns, ifname, expr):
         self.netns, self.ifname, self.expr = netns, ifname, expr