diff options
Diffstat (limited to 'lib/kernel/src/inet_res.erl')
| -rw-r--r-- | lib/kernel/src/inet_res.erl | 53 |
1 files changed, 26 insertions, 27 deletions
diff --git a/lib/kernel/src/inet_res.erl b/lib/kernel/src/inet_res.erl index 962dd82ac9..93563c6011 100644 --- a/lib/kernel/src/inet_res.erl +++ b/lib/kernel/src/inet_res.erl @@ -541,25 +541,32 @@ udp_send(#sock{inet=I}, {A,B,C,D}=IP, Port, Buffer) udp_recv(#sock{inet6=I}, {A,B,C,D,E,F,G,H}=IP, Port, Timeout, Decode) when ?ip6(A,B,C,D,E,F,G,H), ?port(Port) -> - do_udp_recv(I, IP, Port, Timeout, Decode); + do_udp_recv(I, IP, Port, Timeout, Decode, erlang:now(), Timeout); udp_recv(#sock{inet=I}, {A,B,C,D}=IP, Port, Timeout, Decode) when ?ip(A,B,C,D), ?port(Port) -> - do_udp_recv(I, IP, Port, Timeout, Decode). - -do_udp_recv(I, IP, Port, Timeout, Decode) -> - Start = - case Timeout of - 0 -> undefined; - _ -> erlang:now() - end, - do_udp_recv(I, IP, Port, Timeout, Decode, Start, Timeout). + do_udp_recv(I, IP, Port, Timeout, Decode, erlang:now(), Timeout). +do_udp_recv(_I, _IP, _Port, 0, _Decode, _Start, _T) -> + timeout; do_udp_recv(I, IP, Port, Timeout, Decode, Start, T) -> case gen_udp:recv(I, 0, T) of {ok,Reply} -> case Decode(Reply) of - false when Start =:= undefined -> - do_udp_recv(I, IP, Port, Timeout, Decode, Start, T); + false when T =:= 0 -> + %% This is a compromize between the hard way i.e + %% in the clause below if NewT becomes 0 bailout + %% immediately and risk that the right reply lies + %% ahead after some bad id replies, and the + %% forgiving way i.e go on with Timeout 0 until + %% the right reply comes or no reply (timeout) + %% which opens for a DOS attack by a malicious + %% DNS server flooding with bad id replies causing + %% an infinite loop here. + %% + %% Timeout is used as a sanity limit counter + %% just to put an end to the loop. + NewTimeout = erlang:max(0, Timeout - 50), + do_udp_recv(I, IP, Port, NewTimeout, Decode, Start, T); false -> Now = erlang:now(), NewT = erlang:max(0, Timeout - now_ms(Now, Start)), @@ -691,6 +698,8 @@ query_ns(S0, Id, Buffer, IP, Port, Timer, Retry, I, end end. +query_udp(_S, _Id, _Buffer, _IP, _Port, 0, Verbose) -> + timeout; query_udp(S, Id, Buffer, IP, Port, Timeout, Verbose) -> ?verbose(Verbose, "Try UDP server : ~p:~p (timeout=~w)\n", [IP,Port,Timeout]), @@ -716,9 +725,6 @@ query_udp(S, Id, Buffer, IP, Port, Timeout, Verbose) -> case udp_recv(S, IP, Port, Timeout, Decode) of {ok,_}=Result -> Result; - {error,timeout} when Timeout =:= 0 -> - ?verbose(Verbose, "UDP bailout timeout\n", []), - timeout; E2 -> ?verbose(Verbose, "UDP server error: ~p\n", [E2]), E2 @@ -728,6 +734,8 @@ query_udp(S, Id, Buffer, IP, Port, Timeout, Verbose) -> {error,econnrefused} end. +query_tcp(0, _Id, _Buffer, _IP, _Port, Verbose) -> + timeout; query_tcp(Timeout, Id, Buffer, IP, Port, Verbose) -> ?verbose(Verbose, "Try TCP server : ~p:~p (timeout=~w)\n", [IP, Port, Timeout]), @@ -750,19 +758,10 @@ query_tcp(Timeout, Id, Buffer, IP, Port, Verbose) -> end; Error -> gen_tcp:close(S), - case Error of - {error, timeout} when Timeout =:= 0 -> - ?verbose(Verbose, "TCP bailout recv timeout\n", []), - timeout; - _ -> - ?verbose(Verbose, "TCP server recv error: ~p\n", - [Error]), - Error - end + ?verbose(Verbose, "TCP server recv error: ~p\n", + [Error]), + Error end; - {error, timeout} when Timeout =:= 0 -> - ?verbose(Verbose, "TCP bailout connect timeout\n", []), - timeout; Error -> ?verbose(Verbose, "TCP server error: ~p\n", [Error]), Error |