[socket-nif] Add support for socket (level ip) option mtu

Added support for the IP option MTU.

OTP-14831

5 files changed, 44 insertions, 6 deletions

diff --git a/erts/emulator/nifs/common/socket_nif.c b/erts/emulator/nifs/common/socket_nif.c
index 267151083f..6b9f27aa3f 100644
--- a/erts/emulator/nifs/common/socket_nif.c
+++ b/erts/emulator/nifs/common/socket_nif.c
@@ -364,6 +364,7 @@ typedef union {
 
 #define SOCKET_OPT_IP_ADD_MEMBERSHIP   1
 #define SOCKET_OPT_IP_DROP_MEMBERSHIP  5
+#define SOCKET_OPT_IP_MTU             11
 #define SOCKET_OPT_IP_MULTICAST_IF    14
 #define SOCKET_OPT_IP_MULTICAST_LOOP  15
 #define SOCKET_OPT_IP_MULTICAST_TTL   16
@@ -1048,6 +1049,10 @@ static ERL_NIF_TERM ngetopt_lvl_sock_type(ErlNifEnv*        env,
 static ERL_NIF_TERM ngetopt_lvl_ip(ErlNifEnv*        env,
                                    SocketDescriptor* descP,
                                    int               eOpt);
+#if defined(IP_MTU)
+static ERL_NIF_TERM ngetopt_lvl_ip_mtu(ErlNifEnv*        env,
+                                       SocketDescriptor* descP);
+#endif
 #if defined(IP_MULTICAST_IF)
 static ERL_NIF_TERM ngetopt_lvl_ip_multicast_if(ErlNifEnv*        env,
                                                 SocketDescriptor* descP);
@@ -5453,6 +5458,12 @@ ERL_NIF_TERM ngetopt_lvl_ip(ErlNifEnv*        env,
     ERL_NIF_TERM result;
 
     switch (eOpt) {
+#if defined(IP_MTU)
+    case SOCKET_OPT_IP_MTU:
+        result = ngetopt_lvl_ip_mtu(env, descP);
+        break;
+#endif
+
 #if defined(IP_MULTICAST_IF)
     case SOCKET_OPT_IP_MULTICAST_IF:
         result = ngetopt_lvl_ip_multicast_if(env, descP);
@@ -5504,6 +5515,24 @@ ERL_NIF_TERM ngetopt_lvl_ip(ErlNifEnv*        env,
 }
 
 
+/* ngetopt_lvl_ip_mtu - Level IP MTU option
+ */
+#if defined(IP_MTU)
+static
+ERL_NIF_TERM ngetopt_lvl_ip_mtu(ErlNifEnv*        env,
+                                SocketDescriptor* descP)
+{
+#if defined(SOL_IP)
+    int level = SOL_IP;
+#else
+    int level = IPPROTO_IP;
+#endif
+
+    return ngetopt_int_opt(env, descP, level, IP_MTU);
+}
+#endif
+
+
 /* ngetopt_lvl_ip_multicast_if - Level IP MULTICAST_IF option
  */
 #if defined(IP_MULTICAST_IF)
diff --git a/erts/preloaded/ebin/socket.beam b/erts/preloaded/ebin/socket.beam
index f64ea4103b..a172b48cdd 100644
--- a/erts/preloaded/ebin/socket.beam
+++ b/erts/preloaded/ebin/socket.beam
diff --git a/erts/preloaded/src/socket.erl b/erts/preloaded/src/socket.erl
index a4efc2e38c..d6b2289b69 100644
--- a/erts/preloaded/src/socket.erl
+++ b/erts/preloaded/src/socket.erl
@@ -515,14 +515,14 @@
 -define(SOCKET_OPT_IP_ADD_MEMBERSHIP,         1).
 %% -define(SOCKET_OPT_IP_ADD_SOURCE_MEMBERSHIP,  2).
 %% -define(SOCKET_OPT_IP_BLOCK_SOURCE,           3).
-%% -define(SOCKET_OPT_IP_DONT_FRAG,              4).
+%% -define(SOCKET_OPT_IP_DONTFRAG,               4). % Windows? MTU_DISCOVER...
 -define(SOCKET_OPT_IP_DROP_MEMBERSHIP,        5).
 %% -define(SOCKET_OPT_IP_DROP_SOURCE_MEMBERSHIP, 6).
 %% -define(SOCKET_OPT_IP_FREEBIND,               7).
 %% -define(SOCKET_OPT_IP_HDRINCL,                8).
 %% -define(SOCKET_OPT_IP_MINTTL,                 9).
 %% -define(SOCKET_OPT_IP_MSFILTER,              10).
-%% -define(SOCKET_OPT_IP_MTU,                   11).
+-define(SOCKET_OPT_IP_MTU,                   11).
 %% -define(SOCKET_OPT_IP_MTU_DISCOVER,          12).
 %% -define(SOCKET_OPT_IP_MULTICAST_ALL,         13).
 -define(SOCKET_OPT_IP_MULTICAST_IF,          14).
@@ -2275,8 +2275,8 @@ enc_sockopt_key(ip = L, minttl = Opt, _Dir, _D, raw = _T, _P) ->
     not_supported({L, Opt});
 enc_sockopt_key(ip = L, msfilter = Opt, _Dir, _D, _T, _P) ->
     not_supported({L, Opt});
-enc_sockopt_key(ip = L, mtu = Opt, get = _Dir, _D, _T, _P) ->
-    not_supported({L, Opt});
+enc_sockopt_key(ip = _L, mtu = _Opt, get = _Dir, _D, _T, _P) ->
+    ?SOCKET_OPT_IP_MTU;
 enc_sockopt_key(ip = L, mtu_discover = Opt, _Dir, _D, _T, _P) ->
     not_supported({L, Opt});
 enc_sockopt_key(ip = L, multicast_all = Opt, _Dir, _D, _T, _P) ->
diff --git a/lib/kernel/test/socket_client.erl b/lib/kernel/test/socket_client.erl
index 23d3c9956e..dce50682ab 100644
--- a/lib/kernel/test/socket_client.erl
+++ b/lib/kernel/test/socket_client.erl
@@ -80,6 +80,7 @@ do_start(Domain, stream = Type, Proto, SA) ->
             {ok, SndBuf} = socket:getopt(Sock, socket, sndbuf),
             {ok, RcvBuf} = socket:getopt(Sock, socket, rcvbuf),
             {ok, Linger} = socket:getopt(Sock, socket, linger),
+            {ok, MTU}    = socket:getopt(Sock, ip,     mtu),
             {ok, MIF}    = socket:getopt(Sock, ip,     multicast_if),
             {ok, MLoop}  = socket:getopt(Sock, ip,     multicast_loop),
             {ok, MTTL}   = socket:getopt(Sock, ip,     multicast_ttl),
@@ -94,13 +95,14 @@ do_start(Domain, stream = Type, Proto, SA) ->
               "~n   (socket) SndBuf:         ~p"
               "~n   (socket) RcvBuf:         ~p"
               "~n   (socket) Linger:         ~p"
+              "~n   (ip)     MTU:            ~p"
               "~n   (ip)     Multicast IF:   ~p"
               "~n   (ip)     Multicast Loop: ~p"
               "~n   (ip)     Multicast TTL:  ~p"
               "~n   => wait some", 
               [Name, Peer,
                Domain, Type, Proto, 
-               OOBI, SndBuf, RcvBuf, Linger, MIF, MLoop, MTTL]),
+               OOBI, SndBuf, RcvBuf, Linger, MTU, MIF, MLoop, MTTL]),
             %% Give the server some time...
             ?LIB:sleep(5000),
             %% ok = socket:close(Sock),
diff --git a/lib/kernel/test/socket_server.erl b/lib/kernel/test/socket_server.erl
index 5fd32e040c..f77c91996f 100644
--- a/lib/kernel/test/socket_server.erl
+++ b/lib/kernel/test/socket_server.erl
@@ -442,6 +442,12 @@ handler_init(Manager, ID, Peek, Sock) ->
             {ok, SndBuf} = socket:getopt(Sock, socket, sndbuf),
             {ok, RcvBuf} = socket:getopt(Sock, socket, rcvbuf),
             {ok, Linger} = socket:getopt(Sock, socket, linger),
+            MTU = case socket:getopt(Sock, ip, mtu) of
+                      {ok, Val} ->
+                          f("~w", [Val]);
+                      {error, _} ->
+                          "-" % We don't connect UDP (it can be done but we don't)
+                  end,
             {ok, MIF}    = socket:getopt(Sock, ip,     multicast_if),
             {ok, MLoop}  = socket:getopt(Sock, ip,     multicast_loop),
             {ok, MTTL}   = socket:getopt(Sock, ip,     multicast_ttl),
@@ -453,11 +459,12 @@ handler_init(Manager, ID, Peek, Sock) ->
               "~n   (socket) SndBuf:         ~p"
               "~n   (socket) RcvBuf:         ~p"
               "~n   (socket) Linger:         ~p"
+              "~n   (ip)     MTU:            ~s"
               "~n   (ip)     Multicast IF:   ~p"
               "~n   (ip)     Multicast Loop: ~p"
               "~n   (ip)     Multicast TTL:  ~p", 
               [Domain, Type, Proto, 
-               OOBI, SndBuf, RcvBuf, Linger, MIF, MLoop, MTTL]),
+               OOBI, SndBuf, RcvBuf, Linger, MTU, MIF, MLoop, MTTL]),
             %% socket:setopt(Sock, otp, debug, true),
             handler_loop(#handler{peek    = Peek,
                                   manager = Manager,