[3.7] closes bpo-25041: Document AF_PACKET socket address format. (GH-9207)

(cherry picked from commit 731ff68eeef58babdf2b32dc9a73b141760c2be9)

Co-authored-by: Cheryl Sabella <cheryl.sabella@gmail.com>
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index f40bd89..eeade2e 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -1881,7 +1881,7 @@
         const char *interfaceName;
         int protoNumber;
         int hatype = 0;
-        int pkttype = 0;
+        int pkttype = PACKET_HOST;
         Py_buffer haddr = {NULL, NULL};
 
         if (!PyTuple_Check(args)) {
@@ -1912,7 +1912,7 @@
         if (protoNumber < 0 || protoNumber > 0xffff) {
             PyErr_SetString(
                 PyExc_OverflowError,
-                "getsockaddrarg: protoNumber must be 0-65535.");
+                "getsockaddrarg: proto must be 0-65535.");
             PyBuffer_Release(&haddr);
             return 0;
         }
@@ -2925,7 +2925,7 @@
 \n\
 Bind the socket to a local address.  For IP sockets, the address is a\n\
 pair (host, port); the host must refer to the local host. For raw packet\n\
-sockets the address is a tuple (ifname, proto [,pkttype [,hatype]])");
+sockets the address is a tuple (ifname, proto [,pkttype [,hatype [,addr]]])");
 
 
 /* s.close() method.