mirror of https://github.com/mkerrisk/man-pages
ip.7: Reorder socket options alphabetically
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk
parent
119a1824d4
commit
7cd1cc4a53
493
man7/ip.7
493
man7/ip.7
|
|
@ -6,7 +6,7 @@
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.\" and in case of nontrivial modification author and date
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.\" of the modification is added to the header.
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.\" $Id: ip.7,v 1.19 2000/12/20 18:10:31 ak Exp $
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.TH IP 7 2008-10-28 "Linux" "Linux Programmer's Manual"
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.TH IP 7 2008-11-21 "Linux" "Linux Programmer's Manual"
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.SH NAME
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ip \- Linux IPv4 protocol implementation
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.SH SYNOPSIS
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@ -199,6 +199,188 @@ A boolean integer flag is zero when it is false, otherwise true.
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.\" FIXME Document IP_FREEBIND
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.\"
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.TP
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.B IP_ADD_MEMBERSHIP
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Join a multicast group.
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Argument is an
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.I ip_mreqn
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structure.
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.sp
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.in +4n
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.nf
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struct ip_mreqn {
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struct in_addr imr_multiaddr; /* IP multicast group
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address */
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struct in_addr imr_address; /* IP address of local
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interface */
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int imr_ifindex; /* interface index */
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};
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.fi
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.in
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.sp
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.I imr_multiaddr
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contains the address of the multicast group the application
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wants to join or leave.
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It must be a valid multicast address
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||||
.\" (i.e., within the 224.0.0.0-239.255.255.255 range)
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(or
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.BR setsockopt (2)
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fails with the error
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.BR EINVAL ).
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.I imr_address
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is the address of the local interface with which the system
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should join the multicast group; if it is equal to
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.B INADDR_ANY
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an appropriate interface is chosen by the system.
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.I imr_ifindex
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is the interface index of the interface that should join/leave the
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.I imr_multiaddr
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group, or 0 to indicate any interface.
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.IP
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For compatibility, the old
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.I ip_mreq
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structure is still supported.
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It differs from
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.I ip_mreqn
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only by not including the
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.I imr_ifindex
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field.
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Only valid as a
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.BR setsockopt (2).
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.\"
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.TP
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.B IP_DROP_MEMBERSHIP
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Leave a multicast group.
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Argument is an
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.I ip_mreqn
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or
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.I ip_mreq
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structure similar to
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.BR IP_ADD_MEMBERSHIP .
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.TP
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.B IP_HDRINCL
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If enabled,
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the user supplies an IP header in front of the user data.
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Only valid for
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.B SOCK_RAW
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sockets.
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See
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.BR raw (7)
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for more information.
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When this flag is enabled the values set by
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.BR IP_OPTIONS ,
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.B IP_TTL
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and
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.B IP_TOS
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are ignored.
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.TP
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.B IP_MTU
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Retrieve the current known path MTU of the current socket.
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Only valid when the socket has been connected.
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Returns an integer.
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Only valid as a
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.BR getsockopt (2).
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.TP
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.B IP_MTU_DISCOVER
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Sets or receives the Path MTU Discovery setting for a socket.
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When enabled, Linux will perform Path MTU Discovery
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as defined in RFC\ 1191
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on this socket.
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The don't-fragment flag is set on all outgoing datagrams.
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The system-wide default is controlled by the
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.I /proc/sys/net/ipv4/ip_no_pmtu_disc
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file for
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.B SOCK_STREAM
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sockets, and disabled on all others.
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For
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.RB non- SOCK_STREAM
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sockets, it is the user's responsibility to packetize the data
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in MTU sized chunks and to do the retransmits if necessary.
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The kernel will reject packets that are bigger than the known
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path MTU if this flag is set (with
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.B EMSGSIZE
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).
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.TS
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tab(:);
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c l
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l l.
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Path MTU discovery flags:Meaning
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IP_PMTUDISC_WANT:Use per-route settings.
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IP_PMTUDISC_DONT:Never do Path MTU Discovery.
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IP_PMTUDISC_DO:Always do Path MTU Discovery.
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IP_PMTUDISC_PROBE:Set DF but ignore Path MTU.
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.TE
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When PMTU discovery is enabled, the kernel automatically keeps track of
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the path MTU per destination host.
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When it is connected to a specific peer with
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.BR connect (2),
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the currently known path MTU can be retrieved conveniently using the
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.B IP_MTU
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socket option (e.g., after a
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.B EMSGSIZE
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error occurred).
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It may change over time.
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For connectionless sockets with many destinations,
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the new MTU for a given destination can also be accessed using the
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error queue (see
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.BR IP_RECVERR ).
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A new error will be queued for every incoming MTU update.
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While MTU discovery is in progress, initial packets from datagram sockets
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may be dropped.
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Applications using UDP should be aware of this and not
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take it into account for their packet retransmit strategy.
|
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|
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To bootstrap the path MTU discovery process on unconnected sockets, it
|
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is possible to start with a big datagram size
|
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(up to 64K-headers bytes long) and let it shrink by updates of the path MTU.
|
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.\" FIXME this is an ugly hack
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|
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To get an initial estimate of the
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path MTU, connect a datagram socket to the destination address using
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.BR connect (2)
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and retrieve the MTU by calling
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.BR getsockopt (2)
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with the
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.B IP_MTU
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option.
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It is possible to implement RFC 4821 MTU probing with
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.B SOCK_DGRAM
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or
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.B SOCK_RAW
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sockets by setting a value of
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.BR IP_PMTUDISC_PROBE .
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This is also particularly useful for diagnostic tools such as
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.BR tracepath (8)
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that wish to deliberately send probe packets larger than
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the observed Path MTU.
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.TP
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.B IP_MULTICAST_IF
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Set the local device for a multicast socket.
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Argument is an
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.I ip_mreqn
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or
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.I ip_mreq
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structure similar to
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.BR IP_ADD_MEMBERSHIP .
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.IP
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When an invalid socket option is passed,
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.B ENOPROTOOPT
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is returned.
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.TP
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.B IP_MULTICAST_LOOP
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Sets or reads a boolean integer argument that determines whether
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sent multicast packets should be looped back to the local sockets.
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.TP
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.B IP_MULTICAST_TTL
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Set or read the time-to-live value of outgoing multicast packets for this
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socket.
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It is very important for multicast packets to set the smallest TTL possible.
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The default is 1 which means that multicast packets don't leave the local
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network unless the user program explicitly requests it.
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Argument is an integer.
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.TP
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.B IP_OPTIONS
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Sets or get the IP options to be sent with every packet from this socket.
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The arguments are a pointer to a memory buffer containing the options
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@ -277,88 +459,6 @@ index overwrites
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.I ipi_spec_dst
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for the routing table lookup.
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.TP
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.B IP_RECVTOS
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If enabled the
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.B IP_TOS
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ancillary message is passed with incoming packets.
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It contains a byte which specifies the Type of Service/Precedence
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field of the packet header.
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Expects a boolean integer flag.
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.TP
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.B IP_RECVTTL
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When this flag is set, pass a
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.B IP_TTL
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control message with the time to live
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field of the received packet as a byte.
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Not supported for
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.B SOCK_STREAM
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sockets.
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.TP
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.B IP_RECVOPTS
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Pass all incoming IP options to the user in a
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.B IP_OPTIONS
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control message.
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The routing header and other options are already filled in
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for the local host.
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Not supported for
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.B SOCK_STREAM
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sockets.
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.TP
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.B IP_RETOPTS
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Identical to
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.BR IP_RECVOPTS ,
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but returns raw unprocessed options with timestamp and route record
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options not filled in for this hop.
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.TP
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.B IP_TOS
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Set or receive the Type-Of-Service (TOS) field that is sent
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with every IP packet originating from this socket.
|
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It is used to prioritize packets on the network.
|
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TOS is a byte.
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There are some standard TOS flags defined:
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.B IPTOS_LOWDELAY
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to minimize delays for interactive traffic,
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.B IPTOS_THROUGHPUT
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to optimize throughput,
|
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.B IPTOS_RELIABILITY
|
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to optimize for reliability,
|
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.B IPTOS_MINCOST
|
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should be used for "filler data" where slow transmission doesn't matter.
|
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At most one of these TOS values can be specified.
|
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Other bits are invalid and shall be cleared.
|
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Linux sends
|
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.B IPTOS_LOWDELAY
|
||||
datagrams first by default,
|
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but the exact behavior depends on the configured queueing discipline.
|
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.\" FIXME elaborate on this
|
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Some high priority levels may require superuser privileges (the
|
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.B CAP_NET_ADMIN
|
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capability).
|
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The priority can also be set in a protocol independent way by the
|
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.RB ( SOL_SOCKET ", " SO_PRIORITY )
|
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socket option (see
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.BR socket (7)).
|
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.TP
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.B IP_TTL
|
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Set or retrieve the current time-to-live field that is used in every packet
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sent from this socket.
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.TP
|
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.B IP_HDRINCL
|
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If enabled,
|
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the user supplies an IP header in front of the user data.
|
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Only valid for
|
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.B SOCK_RAW
|
||||
sockets.
|
||||
See
|
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.BR raw (7)
|
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for more information.
|
||||
When this flag is enabled the values set by
|
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.BR IP_OPTIONS ,
|
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.B IP_TTL
|
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and
|
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.B IP_TOS
|
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are ignored.
|
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.TP
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.BR IP_RECVERR " (defined in \fI<linux/errqueue.h>\fP)"
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Enable extended reliable error message passing.
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When enabled on a datagram socket, all
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|
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@ -496,89 +596,38 @@ It sets or retrieves an integer boolean flag.
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.B IP_RECVERR
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defaults to off.
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.TP
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.B IP_MTU_DISCOVER
|
||||
Sets or receives the Path MTU Discovery setting for a socket.
|
||||
When enabled, Linux will perform Path MTU Discovery
|
||||
as defined in RFC\ 1191
|
||||
on this socket.
|
||||
The don't-fragment flag is set on all outgoing datagrams.
|
||||
The system-wide default is controlled by the
|
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.I /proc/sys/net/ipv4/ip_no_pmtu_disc
|
||||
file for
|
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.B IP_RECVOPTS
|
||||
Pass all incoming IP options to the user in a
|
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.B IP_OPTIONS
|
||||
control message.
|
||||
The routing header and other options are already filled in
|
||||
for the local host.
|
||||
Not supported for
|
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.B SOCK_STREAM
|
||||
sockets, and disabled on all others.
|
||||
For
|
||||
.RB non- SOCK_STREAM
|
||||
sockets, it is the user's responsibility to packetize the data
|
||||
in MTU sized chunks and to do the retransmits if necessary.
|
||||
The kernel will reject packets that are bigger than the known
|
||||
path MTU if this flag is set (with
|
||||
.B EMSGSIZE
|
||||
).
|
||||
.TS
|
||||
tab(:);
|
||||
c l
|
||||
l l.
|
||||
Path MTU discovery flags:Meaning
|
||||
IP_PMTUDISC_WANT:Use per-route settings.
|
||||
IP_PMTUDISC_DONT:Never do Path MTU Discovery.
|
||||
IP_PMTUDISC_DO:Always do Path MTU Discovery.
|
||||
IP_PMTUDISC_PROBE:Set DF but ignore Path MTU.
|
||||
.TE
|
||||
|
||||
When PMTU discovery is enabled, the kernel automatically keeps track of
|
||||
the path MTU per destination host.
|
||||
When it is connected to a specific peer with
|
||||
.BR connect (2),
|
||||
the currently known path MTU can be retrieved conveniently using the
|
||||
.B IP_MTU
|
||||
socket option (e.g., after a
|
||||
.B EMSGSIZE
|
||||
error occurred).
|
||||
It may change over time.
|
||||
For connectionless sockets with many destinations,
|
||||
the new MTU for a given destination can also be accessed using the
|
||||
error queue (see
|
||||
.BR IP_RECVERR ).
|
||||
A new error will be queued for every incoming MTU update.
|
||||
|
||||
While MTU discovery is in progress, initial packets from datagram sockets
|
||||
may be dropped.
|
||||
Applications using UDP should be aware of this and not
|
||||
take it into account for their packet retransmit strategy.
|
||||
|
||||
To bootstrap the path MTU discovery process on unconnected sockets, it
|
||||
is possible to start with a big datagram size
|
||||
(up to 64K-headers bytes long) and let it shrink by updates of the path MTU.
|
||||
.\" FIXME this is an ugly hack
|
||||
|
||||
To get an initial estimate of the
|
||||
path MTU, connect a datagram socket to the destination address using
|
||||
.BR connect (2)
|
||||
and retrieve the MTU by calling
|
||||
.BR getsockopt (2)
|
||||
with the
|
||||
.B IP_MTU
|
||||
option.
|
||||
|
||||
It is possible to implement RFC 4821 MTU probing with
|
||||
.B SOCK_DGRAM
|
||||
or
|
||||
.B SOCK_RAW
|
||||
sockets by setting a value of
|
||||
.BR IP_PMTUDISC_PROBE .
|
||||
This is also particularly useful for diagnostic tools such as
|
||||
.BR tracepath (8)
|
||||
that wish to deliberately send probe packets larger than
|
||||
the observed Path MTU.
|
||||
sockets.
|
||||
.TP
|
||||
.B IP_MTU
|
||||
Retrieve the current known path MTU of the current socket.
|
||||
Only valid when the socket has been connected.
|
||||
Returns an integer.
|
||||
Only valid as a
|
||||
.BR getsockopt (2).
|
||||
.\"
|
||||
.B IP_RECVTOS
|
||||
If enabled the
|
||||
.B IP_TOS
|
||||
ancillary message is passed with incoming packets.
|
||||
It contains a byte which specifies the Type of Service/Precedence
|
||||
field of the packet header.
|
||||
Expects a boolean integer flag.
|
||||
.TP
|
||||
.B IP_RECVTTL
|
||||
When this flag is set, pass a
|
||||
.B IP_TTL
|
||||
control message with the time to live
|
||||
field of the received packet as a byte.
|
||||
Not supported for
|
||||
.B SOCK_STREAM
|
||||
sockets.
|
||||
.TP
|
||||
.B IP_RETOPTS
|
||||
Identical to
|
||||
.BR IP_RECVOPTS ,
|
||||
but returns raw unprocessed options with timestamp and route record
|
||||
options not filled in for this hop.
|
||||
.TP
|
||||
.B IP_ROUTER_ALERT
|
||||
Pass all to-be forwarded packets with the
|
||||
|
|
@ -590,93 +639,39 @@ the user's responsibility to send them out again.
|
|||
Socket binding is ignored,
|
||||
such packets are only filtered by protocol.
|
||||
Expects an integer flag.
|
||||
.\"
|
||||
.TP
|
||||
.B IP_MULTICAST_TTL
|
||||
Set or read the time-to-live value of outgoing multicast packets for this
|
||||
socket.
|
||||
It is very important for multicast packets to set the smallest TTL possible.
|
||||
The default is 1 which means that multicast packets don't leave the local
|
||||
network unless the user program explicitly requests it.
|
||||
Argument is an integer.
|
||||
.\"
|
||||
.B IP_TOS
|
||||
Set or receive the Type-Of-Service (TOS) field that is sent
|
||||
with every IP packet originating from this socket.
|
||||
It is used to prioritize packets on the network.
|
||||
TOS is a byte.
|
||||
There are some standard TOS flags defined:
|
||||
.B IPTOS_LOWDELAY
|
||||
to minimize delays for interactive traffic,
|
||||
.B IPTOS_THROUGHPUT
|
||||
to optimize throughput,
|
||||
.B IPTOS_RELIABILITY
|
||||
to optimize for reliability,
|
||||
.B IPTOS_MINCOST
|
||||
should be used for "filler data" where slow transmission doesn't matter.
|
||||
At most one of these TOS values can be specified.
|
||||
Other bits are invalid and shall be cleared.
|
||||
Linux sends
|
||||
.B IPTOS_LOWDELAY
|
||||
datagrams first by default,
|
||||
but the exact behavior depends on the configured queueing discipline.
|
||||
.\" FIXME elaborate on this
|
||||
Some high priority levels may require superuser privileges (the
|
||||
.B CAP_NET_ADMIN
|
||||
capability).
|
||||
The priority can also be set in a protocol independent way by the
|
||||
.RB ( SOL_SOCKET ", " SO_PRIORITY )
|
||||
socket option (see
|
||||
.BR socket (7)).
|
||||
.TP
|
||||
.B IP_MULTICAST_LOOP
|
||||
Sets or reads a boolean integer argument that determines whether
|
||||
sent multicast packets should be looped back to the local sockets.
|
||||
.\"
|
||||
.TP
|
||||
.B IP_ADD_MEMBERSHIP
|
||||
Join a multicast group.
|
||||
Argument is an
|
||||
.I ip_mreqn
|
||||
structure.
|
||||
.sp
|
||||
.in +4n
|
||||
.nf
|
||||
struct ip_mreqn {
|
||||
struct in_addr imr_multiaddr; /* IP multicast group
|
||||
address */
|
||||
struct in_addr imr_address; /* IP address of local
|
||||
interface */
|
||||
int imr_ifindex; /* interface index */
|
||||
};
|
||||
.fi
|
||||
.in
|
||||
.sp
|
||||
.I imr_multiaddr
|
||||
contains the address of the multicast group the application
|
||||
wants to join or leave.
|
||||
It must be a valid multicast address
|
||||
.\" (i.e., within the 224.0.0.0-239.255.255.255 range)
|
||||
(or
|
||||
.BR setsockopt (2)
|
||||
fails with the error
|
||||
.BR EINVAL ).
|
||||
.I imr_address
|
||||
is the address of the local interface with which the system
|
||||
should join the multicast group; if it is equal to
|
||||
.B INADDR_ANY
|
||||
an appropriate interface is chosen by the system.
|
||||
.I imr_ifindex
|
||||
is the interface index of the interface that should join/leave the
|
||||
.I imr_multiaddr
|
||||
group, or 0 to indicate any interface.
|
||||
.IP
|
||||
For compatibility, the old
|
||||
.I ip_mreq
|
||||
structure is still supported.
|
||||
It differs from
|
||||
.I ip_mreqn
|
||||
only by not including the
|
||||
.I imr_ifindex
|
||||
field.
|
||||
Only valid as a
|
||||
.BR setsockopt (2).
|
||||
.\"
|
||||
.TP
|
||||
.B IP_DROP_MEMBERSHIP
|
||||
Leave a multicast group.
|
||||
Argument is an
|
||||
.I ip_mreqn
|
||||
or
|
||||
.I ip_mreq
|
||||
structure similar to
|
||||
.BR IP_ADD_MEMBERSHIP .
|
||||
.\"
|
||||
.TP
|
||||
.B IP_MULTICAST_IF
|
||||
Set the local device for a multicast socket.
|
||||
Argument is an
|
||||
.I ip_mreqn
|
||||
or
|
||||
.I ip_mreq
|
||||
structure similar to
|
||||
.BR IP_ADD_MEMBERSHIP .
|
||||
.IP
|
||||
When an invalid socket option is passed,
|
||||
.B ENOPROTOOPT
|
||||
is returned.
|
||||
.B IP_TTL
|
||||
Set or retrieve the current time-to-live field that is used in every packet
|
||||
sent from this socket.
|
||||
.SS /proc interfaces
|
||||
The IP protocol
|
||||
supports a set of
|
||||
|
|
|
|||
Loading…
Reference in New Issue