Split protocols from socket levels

Add a new NIF for retrieving the integer protocol values using atoms.
For socket levels in getsockopt/4 and setsockopt/4, first search
socket_level/1 before checking socket_protocol/1.

socket_protocol/1 duplicates the hard coded values provided by
protocol/1. Since protocol/1 is not exported and is used only with
open/1, it can be replaced with:

    protocol(ip) -> socket_protocol('IPPROTO_IP');
    protocol(icmp) -> socket_protocol('IPPROTO_ICMP');
    protocol(tcp) -> socket_protocol('IPPROTO_TCP');
    ...

Or even:

    protocol(Constant) ->
        socket_protocol(list_to_atom("IPPROTO_" ++
                    string:to_upper(atom_to_list(Constant)))).

c_src/procket.c

@@ -1058,6 +1058,45 @@ nif_socket_optname(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
     return atom_undefined;
 }
 
+    static ERL_NIF_TERM
+nif_socket_protocols(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+    const struct procket_define *p = NULL;
+    ERL_NIF_TERM list = {0};
+
+    list = enif_make_list(env, 0);
+
+    for (p = procket_socket_protocol; p->key != NULL; p++) {
+        list = enif_make_list_cell(
+                env,
+                enif_make_tuple2(
+                    env,
+                    enif_make_atom(env, p->key),
+                    enif_make_uint(env, p->val)
+                    ),
+                list);
+    }
+
+    return list;
+}
+
+    static ERL_NIF_TERM
+nif_socket_protocol(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+    char buf[256] = {0};
+    const struct procket_define *p = NULL;
+
+    if (!enif_get_atom(env, argv[0], buf, sizeof(buf), ERL_NIF_LATIN1))
+        return enif_make_badarg(env);
+
+    for (p = procket_socket_protocol; p->key != NULL; p++) {
+        if (!strcmp(buf, p->key))
+            return enif_make_int(env, p->val);
+    }
+
+    return atom_undefined;
+}
+
 /* 0: errno */
     static ERL_NIF_TERM
 nif_errno_id(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
@@ -1124,8 +1163,10 @@ static ErlNifFunc nif_funcs[] = {
 
     {"socket_level", 0, nif_socket_levels},
     {"socket_optname", 0, nif_socket_optnames},
+    {"socket_protocol", 0, nif_socket_protocols},
     {"socket_level", 1, nif_socket_level},
     {"socket_optname", 1, nif_socket_optname},
+    {"socket_protocol", 1, nif_socket_protocol},
 
     {"errno_id", 1, nif_errno_id}
 };

c_src/procket_constants.h

@@ -3,7 +3,7 @@ struct procket_define {
     int val;
 };
 
-const struct procket_define procket_socket_level[] = {
+const struct procket_define procket_socket_protocol[] = {
 #ifdef IPPROTO_AH
     {"IPPROTO_AH", IPPROTO_AH},
 #endif
@@ -259,6 +259,10 @@ const struct procket_define procket_socket_level[] = {
 #ifdef IPPROTO_XTP
     {"IPPROTO_XTP", IPPROTO_XTP},
 #endif
+    {NULL, -1}
+};
+
+const struct procket_define procket_socket_level[] = {
 #ifdef SOL_AAL
     {"SOL_AAL", SOL_AAL},
 #endif

src/procket.erl

@@ -61,6 +61,7 @@
 
         socket_level/0, socket_level/1,
         socket_optname/0, socket_optname/1,
+        socket_protocol/0, socket_protocol/1,
 
         errno_id/1
     ]).
@@ -187,7 +188,8 @@ sendmsg(_,_,_,_,_) ->
     erlang:nif_error(not_implemented).
 
 setsockopt(Socket,Level,Optname,Optval) when is_atom(Level) ->
-    case socket_level(Level) of
+    case socket_constant_foreach(Level,
+            [fun socket_level/1, fun socket_protocol/1]) of
         undefined ->
             {error,unsupported};
         N ->
@@ -204,7 +206,8 @@ setsockopt(Socket,Level,Optname,Optval) ->
     setsockopt_nif(Socket, Level, Optname, Optval).
 
 getsockopt(Socket,Level,Optname,Optval) when is_atom(Level) ->
-    case socket_level(Level) of
+    case socket_constant_foreach(Level,
+            [fun socket_level/1, fun socket_protocol/1]) of
         undefined ->
             {error,unsupported};
         N ->
@@ -238,9 +241,23 @@ socket_optname() ->
 socket_optname(_) ->
     erlang:nif_error(not_implemented).
 
+socket_protocol() ->
+    erlang:nif_error(not_implemented).
+socket_protocol(_) ->
+    erlang:nif_error(not_implemented).
+
 errno_id(_) ->
     erlang:nif_error(not_implemented).
 
+socket_constant_foreach(_Constant, []) ->
+    undefined;
+socket_constant_foreach(Constant, [Fun|Funs]) ->
+    case Fun(Constant) of
+        undefined ->
+            socket_constant_foreach(Constant, Funs);
+        N when is_integer(N) ->
+            N
+    end.
 
 %%--------------------------------------------------------------------
 %%% Setuid helper