diff options
Diffstat (limited to 'lib/kernel/doc/src/inet.xml')
| -rw-r--r-- | lib/kernel/doc/src/inet.xml | 104 |
1 files changed, 88 insertions, 16 deletions
diff --git a/lib/kernel/doc/src/inet.xml b/lib/kernel/doc/src/inet.xml index 4a3796a15b..fb8bf32978 100644 --- a/lib/kernel/doc/src/inet.xml +++ b/lib/kernel/doc/src/inet.xml @@ -456,47 +456,66 @@ fe80::204:acff:fe17:bf38 <p>Sets one or more options for a socket. The following options are available:</p> <taglist> - <tag><c>{active, true | false | once}</c></tag> + <tag><c>{active, true | false | once | N}</c></tag> <item> <p>If the value is <c>true</c>, which is the default, everything received from the socket will be sent as messages to the receiving process. If the value is <c>false</c> (passive mode), the process must explicitly - receive incoming data by calling <c>gen_tcp:recv/2,3</c> - or <c>gen_udp:recv/2,3</c> (depending on the type of - socket).</p> + receive incoming data by calling + <seealso marker="gen_tcp#recv/2"><c>gen_tcp:recv/2,3</c></seealso>, + <seealso marker="gen_udp#recv/2"><c>gen_udp:recv/2,3</c></seealso> + or <seealso marker="gen_sctp#recv/1"><c>gen_sctp:recv/1,2</c></seealso> + (depending on the type of socket).</p> <p>If the value is <c>once</c> (<c>{active, once}</c>), <em>one</em> data message from the socket will be sent to the process. To receive one more message, <c>setopts/2</c> must be called again with the <c>{active, once}</c> option.</p> - <p>When using <c>{active, once}</c>, the socket changes - behaviour automatically when data is received. This can - sometimes be confusing in combination with connection - oriented sockets (i.e. <c>gen_tcp</c>) as a socket with - <c>{active, false}</c> behaviour reports closing + <p>If the value is an integer <c>N</c> in the range -32768 to 32767 + (inclusive), the value is added to the socket's count of data + messages sent to the controlling process. A socket's default + message count is 0. If a negative value is specified and its + magnitude is equal to or greater than the socket's current + message count, the socket's message count is set to 0. Once + the socket's message count reaches 0, either due to sending + received data messages to the process or by being explicitly set, + the process is then notified by a special message, specific to + the type of socket, that the socket has entered passive + mode. Once the socket enters passive mode, to receive more + messages <c>setopts/2</c> must be called again to set the + socket back into an active mode.</p> + <p>When using <c>{active, once}</c> or <c>{active, N}</c>, the + socket changes behaviour automatically when data is received. + This can sometimes be confusing in combination with + connection-oriented sockets (i.e. <c>gen_tcp</c>) as a socket + with <c>{active, false}</c> behaviour reports closing differently than a socket with <c>{active, true}</c> behaviour. To make programming easier, a socket where the peer closed and this was detected while in <c>{active, false}</c> mode, will still generate the message - <c>{tcp_closed,Socket}</c> when set to <c>{active, once}</c> or <c>{active, true}</c> mode. It is therefore + <c>{tcp_closed,Socket}</c> when set to <c>{active, once}</c>, + <c>{active, true}</c> or <c>{active, N}</c> mode. It is therefore safe to assume that the message <c>{tcp_closed,Socket}</c>, possibly followed by socket port termination (depending on the <c>exit_on_close</c> option) will eventually appear when a socket changes back and forth between <c>{active, true}</c> and - <c>{active, false}</c> mode. However, + <c>{active, false}</c> mode. However, <em>when</em> peer closing is detected is all up to the underlying TCP/IP stack and protocol.</p> - <p>Note that <c>{active,true}</c> mode provides no flow + <p>Note that <c>{active, true}</c> mode provides no flow control; a fast sender could easily overflow the - receiver with incoming messages. Use active mode only if + receiver with incoming messages. The same is true of + <c>{active, N}</c> mode while the message count is greater + than zero. Use active mode only if your high-level protocol provides its own flow control (for instance, acknowledging received messages) or the - amount of data exchanged is small. <c>{active,false}</c> - mode or use of the <c>{active, once}</c> mode provides - flow control; the other side will not be able send + amount of data exchanged is small. <c>{active, false}</c> + mode, use of the <c>{active, once}</c> mode or <c>{active, N}</c> + mode with values of <c>N</c> appropriate for the application + provides flow control; the other side will not be able send faster than the receiver can read.</p> </item> @@ -722,6 +741,59 @@ fe80::204:acff:fe17:bf38 <p>Received <c>Packet</c> is delivered as defined by Mode.</p> </item> + <tag><c>{netns, Namespace :: file:filename_all()}</c></tag> + <item> + <p>Set a network namespace for the socket. The <c>Namespace</c> + parameter is a filename defining the namespace for example + <c>"/var/run/netns/example"</c> typically created by the command + <c>ip netns add example</c>. This option must be used in a + function call that creates a socket i.e + <seealso marker="gen_tcp#connect/3"> + gen_tcp:connect/3,4</seealso>, + <seealso marker="gen_tcp#listen/2"> + gen_tcp:listen/2</seealso>, + <seealso marker="gen_udp#open/1"> + gen_udp:open/1,2</seealso> or + <seealso marker="gen_sctp#open/0"> + gen_sctp:open/0-2</seealso>. + </p> + <p>This option uses the Linux specific syscall + <c>setns()</c> such as in Linux kernel 3.0 or later + and therefore only exists when the runtime system + has been compiled for such an operating system. + </p> + <p> + The virtual machine also needs elevated privileges either + running as superuser or (for Linux) having the capability + <c>CAP_SYS_ADMIN</c> according to the documentation for setns(2). + However, during testing also <c>CAP_SYS_PTRACE</c> + and <c>CAP_DAC_READ_SEARCH</c> has proven to be necessary. + Example:<code> +setcap cap_sys_admin,cap_sys_ptrace,cap_dac_read_search+epi beam.smp +</code> + Note also that the filesystem containing the virtual machine + executable (<c>beam.smp</c> in the example above) has to be local, + mounted without the <c>nosetuid</c> flag, + support extended attributes and that + the kernel has to support file capabilities. + All this runs out of the box on at least Ubuntu 12.04 LTS, + except that SCTP sockets appears to not support + network namespaces. + </p> + <p>The <c>Namespace</c> is a file name and is encoded + and decoded as discussed in + <seealso marker="file">file</seealso> + except that the emulator flag <c>+fnu</c> is ignored and + <seealso marker="#getopts/2">getopts/2</seealso> + for this option will return a binary for the filename + if the stored filename can not be decoded, + which should only happen if you set the option using a binary + that can not be decoded with the emulator's filename encoding: + <seealso marker="file#native_name_encoding/0"> + file:native_name_encoding/0</seealso>. + </p> + </item> + <tag><c>list</c></tag> <item> <p>Received <c>Packet</c> is delivered as a list.</p> |