Test for sniffing packets

Export pcap_lookup().

README.md

@@ -138,6 +138,10 @@ SMP erlang must be enabled (erl -smp -pa ebin).
 
         Write the packet to the network. See pcap_sendpacket(3PCAP).
 
+    dev() -> {ok, string()} | {error, pcap_error_string()}
+
+        Returns the default device used by PCAP.
+
     getifaddrs() -> {ok, Iflist} | {error, posix()}
 
         Types   Iflist = [{Ifname, [Ifopt]}]

src/ewpcap.erl

@@ -37,7 +37,7 @@
     filter/2, filter/3,
     read/1, read/2,
     write/2,
-    getifaddrs/0
+    getifaddrs/0, dev/0
     ]).
 
 -define(PCAP_NETMASK_UNKNOWN, 16#ffffffff).
@@ -148,6 +148,9 @@ read(#ewpcap_resource{ref = Ref}, Timeout) ->
 write(#ewpcap_resource{res = Res}, Data) when is_list(Data); is_binary(Data) ->
     pcap_sendpacket(Res, Data).
 
+dev() ->
+    pcap_lookupdev().
+
 getifaddrs() ->
     case pcap_findalldevs() of
         {ok, Iflist} ->

test/ewpcap_tests.erl

@@ -35,6 +35,29 @@
 -include_lib("eunit/include/eunit.hrl").
 -include("ewpcap.hrl").
 
+open_test() ->
+    case ewpcap:getifaddrs() of
+        {ok, []} ->
+            error_logger:info_report([
+                {skipping, "beam does not have privileges to run test"}
+            ]),
+            ok;
+        {ok, _Iflist} ->
+            open_test_1()
+    end.
+
+open_test_1() ->
+    {ok, Ifname} = ewpcap:dev(),
+    {ok, Socket} = ewpcap:open(Ifname, [{filter, "tcp and port 29"}]),
+
+    {error, eagain} = ewpcap:read(Socket, 100),
+    gen_tcp:connect({8,8,8,8}, 29, [binary], 100),
+    {ok, Packet} = ewpcap:read(Socket),
+
+    error_logger:info_report([{got, Packet}]),
+
+    ok.
+
 getifaddrs_test() ->
     case os:type() of
         {unix, _} ->