freebsd-skq/share/man/man4/udp.4
Andrey V. Elsukov fcf596178b Merge projects/ipsec into head/.
Small summary
 -------------

o Almost all IPsec releated code was moved into sys/netipsec.
o New kernel modules added: ipsec.ko and tcpmd5.ko. New kernel
  option IPSEC_SUPPORT added. It enables support for loading
  and unloading of ipsec.ko and tcpmd5.ko kernel modules.
o IPSEC_NAT_T option was removed. Now NAT-T support is enabled by
  default. The UDP_ENCAP_ESPINUDP_NON_IKE encapsulation type
  support was removed. Added TCP/UDP checksum handling for
  inbound packets that were decapsulated by transport mode SAs.
  setkey(8) modified to show run-time NAT-T configuration of SA.
o New network pseudo interface if_ipsec(4) added. For now it is
  build as part of ipsec.ko module (or with IPSEC kernel).
  It implements IPsec virtual tunnels to create route-based VPNs.
o The network stack now invokes IPsec functions using special
  methods. The only one header file <netipsec/ipsec_support.h>
  should be included to declare all the needed things to work
  with IPsec.
o All IPsec protocols handlers (ESP/AH/IPCOMP protosw) were removed.
  Now these protocols are handled directly via IPsec methods.
o TCP_SIGNATURE support was reworked to be more close to RFC.
o PF_KEY SADB was reworked:
  - now all security associations stored in the single SPI namespace,
    and all SAs MUST have unique SPI.
  - several hash tables added to speed up lookups in SADB.
  - SADB now uses rmlock to protect access, and concurrent threads
    can do SA lookups in the same time.
  - many PF_KEY message handlers were reworked to reflect changes
    in SADB.
  - SADB_UPDATE message was extended to support new PF_KEY headers:
    SADB_X_EXT_NEW_ADDRESS_SRC and SADB_X_EXT_NEW_ADDRESS_DST. They
    can be used by IKE daemon to change SA addresses.
o ipsecrequest and secpolicy structures were cardinally changed to
  avoid locking protection for ipsecrequest. Now we support
  only limited number (4) of bundled SAs, but they are supported
  for both INET and INET6.
o INPCB security policy cache was introduced. Each PCB now caches
  used security policies to avoid SP lookup for each packet.
o For inbound security policies added the mode, when the kernel does
  check for full history of applied IPsec transforms.
o References counting rules for security policies and security
  associations were changed. The proper SA locking added into xform
  code.
o xform code was also changed. Now it is possible to unregister xforms.
  tdb_xxx structures were changed and renamed to reflect changes in
  SADB/SPDB, and changed rules for locking and refcounting.

Reviewed by:	gnn, wblock
Obtained from:	Yandex LLC
Relnotes:	yes
Sponsored by:	Yandex LLC
Differential Revision:	https://reviews.freebsd.org/D9352
2017-02-06 08:49:57 +00:00

179 lines
4.7 KiB
Groff

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.\" @(#)udp.4 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
.Dd February 6, 2017
.Dt UDP 4
.Os
.Sh NAME
.Nm udp
.Nd Internet User Datagram Protocol
.Sh SYNOPSIS
.In sys/types.h
.In sys/socket.h
.In netinet/in.h
.Ft int
.Fn socket AF_INET SOCK_DGRAM 0
.Sh DESCRIPTION
.Tn UDP
is a simple, unreliable datagram protocol which is used
to support the
.Dv SOCK_DGRAM
abstraction for the Internet
protocol family.
.Tn UDP
sockets are connectionless, and are
normally used with the
.Xr sendto 2
and
.Xr recvfrom 2
calls, though the
.Xr connect 2
call may also be used to fix the destination for future
packets (in which case the
.Xr recv 2
or
.Xr read 2
and
.Xr send 2
or
.Xr write 2
system calls may be used).
.Pp
.Tn UDP
address formats are identical to those used by
.Tn TCP .
In particular
.Tn UDP
provides a port identifier in addition
to the normal Internet address format.
Note that the
.Tn UDP
port
space is separate from the
.Tn TCP
port space (i.e., a
.Tn UDP
port
may not be
.Dq connected
to a
.Tn TCP
port).
In addition broadcast
packets may be sent (assuming the underlying network supports
this) by using a reserved
.Dq broadcast address ;
this address
is network interface dependent.
.Pp
Options at the
.Tn IP
transport level may be used with
.Tn UDP ;
see
.Xr ip 4 .
.Tn UDP_ENCAP
socket option may be used at the
.Tn IPPROTO_UDP
level to encapsulate
.Tn ESP
packets in
.Tn UDP .
Only one value is supported for this option:
.Tn UDP_ENCAP_ESPINUDP
from RFC 3948, defined in
.In netinet/udp.h .
.Sh MIB VARIABLES
The
.Nm
protocol implements a number of variables in the
.Li net.inet
branch of the
.Xr sysctl 3
MIB.
.Bl -tag -width UDPCTL_RECVSPACEX
.It UDPCTL_CHECKSUM
.Pq udp.checksum
Enable udp checksums (enabled by default).
.It UDPCTL_MAXDGRAM
.Pq udp.maxdgram
Maximum outgoing UDP datagram size
.It UDPCTL_RECVSPACE
.Pq udp.recvspace
Maximum space for incoming UDP datagrams
.It udp.log_in_vain
For all udp datagrams, to ports on which there is no socket
listening, log the connection attempt (disabled by default).
.It udp.blackhole
When a datagram is received on a port where there is no socket
listening, do not return an ICMP port unreachable message.
(Disabled by default.
See
.Xr blackhole 4 . )
.El
.Sh ERRORS
A socket operation may fail with one of the following errors returned:
.Bl -tag -width Er
.It Bq Er EISCONN
when trying to establish a connection on a socket which
already has one, or when trying to send a datagram with the destination
address specified and the socket is already connected;
.It Bq Er ENOTCONN
when trying to send a datagram, but
no destination address is specified, and the socket has not been
connected;
.It Bq Er ENOBUFS
when the system runs out of memory for
an internal data structure;
.It Bq Er EADDRINUSE
when an attempt
is made to create a socket with a port which has already been
allocated;
.It Bq Er EADDRNOTAVAIL
when an attempt is made to create a
socket with a network address for which no network interface
exists.
.El
.Sh SEE ALSO
.Xr getsockopt 2 ,
.Xr recv 2 ,
.Xr send 2 ,
.Xr socket 2 ,
.Xr blackhole 4 ,
.Xr inet 4 ,
.Xr intro 4 ,
.Xr ip 4 ,
.Xr udplite 4
.Sh HISTORY
The
.Nm
protocol appeared in
.Bx 4.2 .