[PD] Support get local ip from NIC for PD disaggregation (#7237)

Signed-off-by: Shangming Cai <caishangming@linux.alibaba.com>

python/sglang/srt/utils.py

@@ -2141,6 +2141,44 @@ def get_free_port():
             return s.getsockname()[1]
 
 
+def get_local_ip_auto() -> str:
+    interface = os.environ.get("SGLANG_LOCAL_IP_NIC", None)
+    return (
+        get_local_ip_by_nic(interface)
+        if interface is not None
+        else get_local_ip_by_remote()
+    )
+
+
+def get_local_ip_by_nic(interface: str) -> str:
+    try:
+        import netifaces
+    except ImportError as e:
+        raise ImportError(
+            "Environment variable SGLANG_LOCAL_IP_NIC requires package netifaces, please install it through 'pip install netifaces'"
+        ) from e
+
+    try:
+        addresses = netifaces.ifaddresses(interface)
+        if netifaces.AF_INET in addresses:
+            for addr_info in addresses[netifaces.AF_INET]:
+                ip = addr_info.get("addr")
+                if ip and ip != "127.0.0.1" and ip != "0.0.0.0":
+                    return ip
+        if netifaces.AF_INET6 in addresses:
+            for addr_info in addresses[netifaces.AF_INET6]:
+                ip = addr_info.get("addr")
+                if ip and not ip.startswith("fe80::") and ip != "::1":
+                    return ip.split("%")[0]
+    except (ValueError, OSError) as e:
+        raise ValueError(
+            "Can not get local ip from NIC. Please verify whether SGLANG_LOCAL_IP_NIC is set correctly."
+        )
+
+    # Fallback
+    return get_local_ip_by_remote()
+
+
 def get_local_ip_by_remote() -> str:
     # try ipv4
     s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)