diff options
Diffstat (limited to 'man7/tcp.7')
| -rw-r--r-- | man7/tcp.7 | 136 |
1 files changed, 68 insertions, 68 deletions
diff --git a/man7/tcp.7 b/man7/tcp.7 index c7b393c10..b65dd1f51 100644 --- a/man7/tcp.7 +++ b/man7/tcp.7 @@ -105,7 +105,7 @@ RFC\ 793, RFC\ 1122 and RFC\ 2001 with the NewReno and SACK extensions. It provides a reliable, stream-oriented, full-duplex connection between two sockets on top of -.BR ip (7), +.MR ip 7 , for both v4 and v6 versions. TCP guarantees that the data arrives in order and retransmits lost packets. @@ -116,19 +116,19 @@ TCP does not preserve record boundaries. A newly created TCP socket has no remote or local address and is not fully specified. To create an outgoing TCP connection use -.BR connect (2) +.MR connect 2 to establish a connection to another TCP socket. To receive new incoming connections, first -.BR bind (2) +.MR bind 2 the socket to a local address and port and then call -.BR listen (2) +.MR listen 2 to put the socket into the listening state. After that a new socket for each incoming connection can be accepted using -.BR accept (2). +.MR accept 2 . A socket which has had -.BR accept (2) +.MR accept 2 or -.BR connect (2) +.MR connect 2 successfully called on it is fully specified and may transmit data. Data cannot be transmitted on listening or not yet connected sockets. .P @@ -149,7 +149,7 @@ files, or on individual sockets by using the and .B SO_RCVBUF socket options with the -.BR setsockopt (2) +.MR setsockopt 2 call. .P The maximum sizes for socket buffers declared via the @@ -163,11 +163,11 @@ and files. Note that TCP actually allocates twice the size of the buffer requested in the -.BR setsockopt (2) +.MR setsockopt 2 call, and so a succeeding -.BR getsockopt (2) +.MR getsockopt 2 call will not return the same size of buffer as requested in the -.BR setsockopt (2) +.MR setsockopt 2 call. TCP uses the extra space for administrative purposes and internal kernel structures, and the @@ -175,12 +175,12 @@ kernel structures, and the file values reflect the larger sizes compared to the actual TCP windows. On individual connections, the socket buffer size must be set prior to the -.BR listen (2) +.MR listen 2 or -.BR connect (2) +.MR connect 2 calls in order to have it take effect. See -.BR socket (7) +.MR socket 7 for more information. .P TCP supports urgent data. @@ -190,7 +190,7 @@ stream and that it should be processed as soon as possible. To send urgent data specify the .B MSG_OOB option to -.BR send (2). +.MR send 2 . When urgent data is received, the kernel sends a .B SIGURG signal to the process or process group that has been set as the @@ -199,7 +199,7 @@ socket "owner" using the or .B FIOSETOWN ioctls (or the POSIX.1-specified -.BR fcntl (2) +.MR fcntl 2 .B F_SETOWN operation). When the @@ -211,12 +211,12 @@ ioctl described below), otherwise it can be received only when the .B MSG_OOB flag is set for -.BR recv (2) +.MR recv 2 or -.BR recvmsg (2). +.MR recvmsg 2 . .P When out-of-band data is present, -.BR select (2) +.MR select 2 indicates the file descriptor as having an exceptional condition and .I poll (2) indicates a @@ -226,15 +226,15 @@ event. Linux 2.4 introduced a number of changes for improved throughput and scaling, as well as enhanced functionality. Some of these features include support for zero-copy -.BR sendfile (2), +.MR sendfile 2 , Explicit Congestion Notification, new management of TIME_WAIT sockets, keep-alive socket options and support for Duplicate SACK extensions. .SS Address formats TCP is built on top of IP (see -.BR ip (7)). +.MR ip 7 ). The address formats defined by -.BR ip (7) +.MR ip 7 apply to TCP. TCP supports point-to-point communication only; broadcasting and multicasting are not @@ -245,7 +245,7 @@ System-wide TCP parameter settings can be accessed by files in the directory In addition, most IP .I /proc interfaces also apply to TCP; see -.BR ip (7). +.MR ip 7 . Variables described as .I Boolean take an integer value, with a nonzero value ("true") meaning that @@ -335,9 +335,9 @@ The default value for this list is "reno" plus the default setting of .\" Text heavily based on Documentation/networking/ip-sysctl.txt If this option is enabled, the kernel tries to coalesce small writes (from consecutive -.BR write (2) +.MR write 2 and -.BR sendmsg (2) +.MR sendmsg 2 calls) as much as possible, in order to decrease the total number of sent packets. Coalescing is done if at least one prior packet for the flow @@ -1052,9 +1052,9 @@ If disabled, assume that the remote TCP is not broken even if we do not receive a window scaling option from it. .SS Socket options To set or get a TCP socket option, call -.BR getsockopt (2) +.MR getsockopt 2 to read or -.BR setsockopt (2) +.MR setsockopt 2 to write the option with the option level argument set to .BR IPPROTO_TCP . Unless otherwise noted, @@ -1067,12 +1067,12 @@ most .B IPPROTO_IP socket options are valid on TCP sockets. For more information see -.BR ip (7). +.MR ip 7 . .P Following is a list of TCP-specific socket options. For details of some other socket options that are also applicable for TCP sockets, see -.BR socket (7). +.MR socket 7 . .TP .BR TCP_CONGESTION " (since Linux 2.6.13)" .\" commit 5f8ef48d240963093451bcf83df89f1a1364f51d @@ -1095,7 +1095,7 @@ above). If set, don't send out partial frames. All queued partial frames are sent when the option is cleared again. This is useful for prepending headers before calling -.BR sendfile (2), +.MR sendfile 2 , or for throughput optimization. As currently implemented, there is a 200 millisecond ceiling on the time for which output is corked by @@ -1151,7 +1151,7 @@ This option can be used to override the system-wide setting in the file .I /proc/sys/net/ipv4/tcp_fin_timeout for this socket. This is not to be confused with the -.BR socket (7) +.MR socket 7 level option .BR SO_LINGER . This option should not be used in code intended to be portable. @@ -1245,7 +1245,7 @@ The option has no effect on when TCP retransmits a packet, nor when a keepalive probe is sent. .IP This option, like many others, will be inherited by the socket returned by -.BR accept (2), +.MR accept 2 , if it was set on the listening socket. .IP Further details on the user timeout feature can be found in @@ -1262,14 +1262,14 @@ portable. This option enables Fast Open (RFC\~7413) on the listener socket. The value specifies the maximum length of pending SYNs (similar to the backlog argument in -.BR listen (2)). +.MR listen 2 ). Once enabled, the listener socket grants the TCP Fast Open cookie on incoming SYN with TCP Fast Open option. .IP More importantly it accepts the data in SYN with a valid Fast Open cookie and responds SYN-ACK acknowledging both the data and the SYN sequence. -.BR accept (2) +.MR accept 2 returns a socket that is available for read and write when the handshake has not completed yet. Thus the data exchange can commence before the handshake completes. @@ -1278,7 +1278,7 @@ This option requires enabling the server-side support on sysctl (see above). For TCP Fast Open client-side support, see -.BR send (2) +.MR send 2 .B MSG_FASTOPEN or .B TCP_FASTOPEN_CONNECT @@ -1288,23 +1288,23 @@ below. This option enables an alternative way to perform Fast Open on the active side (client). When this option is enabled, -.BR connect (2) +.MR connect 2 would behave differently depending on if a Fast Open cookie is available for the destination. .IP If a cookie is not available (i.e. first contact to the destination), -.BR connect (2) +.MR connect 2 behaves as usual by sending a SYN immediately, except the SYN would include an empty Fast Open cookie option to solicit a cookie. .IP If a cookie is available, -.BR connect (2) +.MR connect 2 would return 0 immediately but the SYN transmission is deferred. A subsequent -.BR write (2) +.MR write 2 or -.BR sendmsg (2) +.MR sendmsg 2 would trigger a SYN with data plus cookie in the Fast Open option. In other words, the actual connect operation is deferred until data is supplied. @@ -1316,30 +1316,30 @@ different .I errno values. With cookie present, -.BR write (2) +.MR write 2 or -.BR sendmsg (2) +.MR sendmsg 2 must be called right after -.BR connect (2) +.MR connect 2 in order to send out SYN+data to complete 3WHS and establish connection. Calling -.BR read (2) +.MR read 2 right after -.BR connect (2) +.MR connect 2 without -.BR write (2) +.MR write 2 will cause the blocking socket to be blocked forever. .IP The application should either set .B TCP_FASTOPEN_CONNECT socket option before -.BR write (2) +.MR write 2 or -.BR sendmsg (2), +.MR sendmsg 2 , or call -.BR write (2) +.MR write 2 or -.BR sendmsg (2) +.MR sendmsg 2 with .B MSG_FASTOPEN flag directly, @@ -1377,7 +1377,7 @@ It can be changed via .IR /proc/sys/net/ipv4/tcp_stdurg . .P It is possible to peek at out-of-band data using the -.BR recv (2) +.MR recv 2 .B MSG_PEEK flag. .P @@ -1386,9 +1386,9 @@ Since Linux 2.4, Linux supports the use of in the .I flags argument of -.BR recv (2) +.MR recv 2 (and -.BR recvmsg (2)). +.MR recvmsg 2 ). This flag causes the received bytes of data to be discarded, rather than passed back in a caller-supplied buffer. Since Linux 2.4.4, @@ -1398,7 +1398,7 @@ also has this effect when used in conjunction with to receive out-of-band data. .SS Ioctls The following -.BR ioctl (2) +.MR ioctl 2 calls return information in .IR value . The correct syntax is: @@ -1452,7 +1452,7 @@ flag). .IP Note that a read never reads across the urgent mark. If an application is informed of the presence of urgent data via -.BR select (2) +.MR select 2 (using the .I exceptfds argument) or through delivery of a @@ -1511,11 +1511,11 @@ executed on a shut down socket. The other end didn't acknowledge retransmitted data after some time. .P Any errors defined for -.BR ip (7) +.MR ip 7 or the generic socket layer may also be returned for TCP. .SH VERSIONS Support for Explicit Congestion Notification, zero-copy -.BR sendfile (2), +.MR sendfile 2 , reordering support and some SACK extensions (DSACK) were introduced in Linux 2.4. Support for forward acknowledgement (FACK), TIME_WAIT recycling, @@ -1533,17 +1533,17 @@ IPv6 is not described. .\" Alexey Kuznetsov's Documentation/networking/ip-sysctl.txt .\" document. .SH SEE ALSO -.BR accept (2), -.BR bind (2), -.BR connect (2), -.BR getsockopt (2), -.BR listen (2), -.BR recvmsg (2), -.BR sendfile (2), -.BR sendmsg (2), -.BR socket (2), -.BR ip (7), -.BR socket (7) +.MR accept 2 , +.MR bind 2 , +.MR connect 2 , +.MR getsockopt 2 , +.MR listen 2 , +.MR recvmsg 2 , +.MR sendfile 2 , +.MR sendmsg 2 , +.MR socket 2 , +.MR ip 7 , +.MR socket 7 .P The kernel source file .IR Documentation/networking/ip\-sysctl.txt . |