fix(get_config): strip veth interfaces — Docker container churn causes false-positive config changes every poll

Docker creates a fresh veth pair with a new random name and ifindex
for every container start/restart. ip addr show includes them, so
get_config() reported a "config change" on nearly every poll of a
Docker host even though nothing about the host's own configuration
changed.

napalm_linux/linux.py

@@ -697,13 +697,19 @@ class LinuxDriver(OSDriver):
 
         ``valid_lft`` / ``preferred_lft`` fields from DHCP leases are stripped
         so the output is stable across polls and does not produce false-positive
-        config-change events in the config-backup feature.
+        config-change events in the config-backup feature. ``veth*`` interfaces
+        are stripped entirely — Docker creates/destroys them with a fresh index
+        and random name on every container restart, which would otherwise flag
+        a config change on nearly every poll of a Docker host.
         """
         import re
 
         running = self._send("ip addr show && ip route show")
         # Strip volatile DHCP lease timer fields — they decrement every poll
         running = re.sub(r"\s+valid_lft\s+\S+\s+preferred_lft\s+\S+", "", running)
+        # Strip veth interface blocks (line + indented sub-lines) — ephemeral
+        # Docker container network endpoints, not intentional host config
+        running = re.sub(r"^\d+: veth\S*:.*\n(?:[ \t]+.*\n?)*", "", running, flags=re.MULTILINE)
         return {"running": running, "startup": "", "candidate": ""}
 
     # ------------------------------------------------------------------

tests/test_linux.py

@@ -88,6 +88,46 @@ def test_get_interfaces_parses_state(driver):
     assert result["eth1"]["is_up"] is False
 
 
+# ---------------------------------------------------------------------------
+# get_config
+# ---------------------------------------------------------------------------
+
+
+IP_ADDR_ROUTE_WITH_VETH = """\
+1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
+    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+    inet 127.0.0.1/8 scope host lo
+       valid_lft forever preferred_lft forever
+2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
+    link/ether aa:bb:cc:dd:ee:ff brd ff:ff:ff:ff:ff:ff
+    inet 192.168.1.10/24 brd 192.168.1.255 scope global dynamic eth0
+       valid_lft 3542sec preferred_lft 3542sec
+3512: veth5d7e34d@if2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-ebb930396f3b state UP group default
+    link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0
+default via 192.168.1.1 dev eth0
+192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.10
+"""
+
+
+def test_get_config_strips_dhcp_lease_timers(driver):
+    with patch.object(driver, "_send", return_value=IP_ADDR_ROUTE_WITH_VETH):
+        result = driver.get_config()
+    assert "valid_lft" not in result["running"]
+    assert "preferred_lft" not in result["running"]
+
+
+def test_get_config_strips_veth_interfaces(driver):
+    """Docker creates/destroys veth pairs on every container restart — including
+    them would make get_config() report a false-positive change on every poll."""
+    with patch.object(driver, "_send", return_value=IP_ADDR_ROUTE_WITH_VETH):
+        result = driver.get_config()
+    assert "veth5d7e34d" not in result["running"]
+    assert "3512:" not in result["running"]
+    # Real interfaces and routes must survive the filter
+    assert "eth0" in result["running"]
+    assert "default via 192.168.1.1" in result["running"]
+
+
 # ---------------------------------------------------------------------------
 # _parse_uptime
 # ---------------------------------------------------------------------------