Add support for getsockopt(2)

README.md

@@ -196,6 +196,21 @@ procket works with any version of Erlang after R14A.
 
         See setsockopt(2).
 
+    getsockopt(Socket, Level, Optname, Optval) -> {ok, Buf} | {error, posix}
+
+        Types   Socket = integer()
+                Level = integer()
+                Optname = integer()
+                Optval = binary()
+                Buf = binary()
+
+        See getsockopt(2). Similar to inet:getopts/2 but can be used
+        with file descriptors.
+
+        Retrieve a socket option for a file descriptor. Use an empty
+        binary to indicate no option value is supplied or will be
+        returned.
+
     ioctl(FD, Request, Arg) -> {ok, Result} | {error, posix()}
 
         Types   FD = integer()

c_src/procket.c

@@ -535,6 +535,48 @@ nif_setsockopt(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
     return atom_ok;
 }
 
+/* 0: int socket descriptor, 1: int level,
+ * 2: int optname, 3: void *optval
+ */
+    static ERL_NIF_TERM
+nif_getsockopt(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
+{
+    int s = -1;
+    int level = 0;
+    int optname = 0;
+    ErlNifBinary optval = {0};
+    socklen_t optlen = 0;
+
+
+    if (!enif_get_int(env, argv[0], &s))
+        return enif_make_badarg(env);
+
+    if (!enif_get_int(env, argv[1], &level))
+        return enif_make_badarg(env);
+
+    if (!enif_get_int(env, argv[2], &optname))
+        return enif_make_badarg(env);
+
+    if (!enif_inspect_binary(env, argv[3], &optval))
+        return enif_make_badarg(env);
+
+    /* Make the binary mutable */
+    if (!enif_realloc_binary(&optval, optval.size))
+        return error_tuple(env, ENOMEM);
+
+    optlen = optval.size;
+
+    if (getsockopt(s, level, optname,
+                (optval.size == 0 ? NULL : optval.data), &optlen) < 0)
+        return error_tuple(env, errno);
+
+    PROCKET_REALLOC(optval, optlen);
+
+    return enif_make_tuple2(env,
+            atom_ok,
+            enif_make_binary(env, &optval));
+}
+
 
 // int getsockname(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
     static ERL_NIF_TERM
@@ -745,6 +787,7 @@ static ErlNifFunc nif_funcs[] = {
     {"connect", 2, nif_connect},
     {"listen", 2, nif_listen},
     {"getsockname", 2, nif_getsockname},
+    {"getsockopt", 4, nif_getsockopt},
     {"ioctl", 3, nif_ioctl},
     {"socket_nif", 3, nif_socket},
     {"recvfrom", 4, nif_recvfrom},

src/procket.erl

@@ -47,6 +47,7 @@
         bind/2,
         ioctl/3,
         setsockopt/4,
+        getsockopt/4,
         getsockname/2,
 
         alloc/1,
@@ -157,6 +158,9 @@ writev(_,_) ->
 setsockopt(_,_,_,_) ->
     erlang:error(not_implemented).
 
+getsockopt(_,_,_,_) ->
+    erlang:error(not_implemented).
+
 getsockname(_,_) ->
     erlang:error(not_implemented).