65cb6b6834
This particular implementation is designed to be fully backwards compatible
and to be MFC-able to 7.x (and 6.x)
Currently the only protocol that can make use of the multiple tables is IPv4
Similar functionality exists in OpenBSD and Linux.
From my notes:
-----
One thing where FreeBSD has been falling behind, and which by chance I
have some time to work on is "policy based routing", which allows
different
packet streams to be routed by more than just the destination address.
Constraints:
------------
I want to make some form of this available in the 6.x tree
(and by extension 7.x) , but FreeBSD in general needs it so I might as
well do it in -current and back port the portions I need.
One of the ways that this can be done is to have the ability to
instantiate multiple kernel routing tables (which I will now
refer to as "Forwarding Information Bases" or "FIBs" for political
correctness reasons). Which FIB a particular packet uses to make
the next hop decision can be decided by a number of mechanisms.
The policies these mechanisms implement are the "Policies" referred
to in "Policy based routing".
One of the constraints I have if I try to back port this work to
6.x is that it must be implemented as a EXTENSION to the existing
ABIs in 6.x so that third party applications do not need to be
recompiled in timespan of the branch.
This first version will not have some of the bells and whistles that
will come with later versions. It will, for example, be limited to 16
tables in the first commit.
Implementation method, Compatible version. (part 1)
-------------------------------
For this reason I have implemented a "sufficient subset" of a
multiple routing table solution in Perforce, and back-ported it
to 6.x. (also in Perforce though not always caught up with what I
have done in -current/P4). The subset allows a number of FIBs
to be defined at compile time (8 is sufficient for my purposes in 6.x)
and implements the changes needed to allow IPV4 to use them. I have not
done the changes for ipv6 simply because I do not need it, and I do not
have enough knowledge of ipv6 (e.g. neighbor discovery) needed to do it.
Other protocol families are left untouched and should there be
users with proprietary protocol families, they should continue to work
and be oblivious to the existence of the extra FIBs.
To understand how this is done, one must know that the current FIB
code starts everything off with a single dimensional array of
pointers to FIB head structures (One per protocol family), each of
which in turn points to the trie of routes available to that family.
The basic change in the ABI compatible version of the change is to
extent that array to be a 2 dimensional array, so that
instead of protocol family X looking at rt_tables[X] for the
table it needs, it looks at rt_tables[Y][X] when for all
protocol families except ipv4 Y is always 0.
Code that is unaware of the change always just sees the first row
of the table, which of course looks just like the one dimensional
array that existed before.
The entry points rtrequest(), rtalloc(), rtalloc1(), rtalloc_ign()
are all maintained, but refer only to the first row of the array,
so that existing callers in proprietary protocols can continue to
do the "right thing".
Some new entry points are added, for the exclusive use of ipv4 code
called in_rtrequest(), in_rtalloc(), in_rtalloc1() and in_rtalloc_ign(),
which have an extra argument which refers the code to the correct row.
In addition, there are some new entry points (currently called
rtalloc_fib() and friends) that check the Address family being
looked up and call either rtalloc() (and friends) if the protocol
is not IPv4 forcing the action to row 0 or to the appropriate row
if it IS IPv4 (and that info is available). These are for calling
from code that is not specific to any particular protocol. The way
these are implemented would change in the non ABI preserving code
to be added later.
One feature of the first version of the code is that for ipv4,
the interface routes show up automatically on all the FIBs, so
that no matter what FIB you select you always have the basic
direct attached hosts available to you. (rtinit() does this
automatically).
You CAN delete an interface route from one FIB should you want
to but by default it's there. ARP information is also available
in each FIB. It's assumed that the same machine would have the
same MAC address, regardless of which FIB you are using to get
to it.
This brings us as to how the correct FIB is selected for an outgoing
IPV4 packet.
Firstly, all packets have a FIB associated with them. if nothing
has been done to change it, it will be FIB 0. The FIB is changed
in the following ways.
Packets fall into one of a number of classes.
1/ locally generated packets, coming from a socket/PCB.
Such packets select a FIB from a number associated with the
socket/PCB. This in turn is inherited from the process,
but can be changed by a socket option. The process in turn
inherits it on fork. I have written a utility call setfib
that acts a bit like nice..
setfib -3 ping target.example.com # will use fib 3 for ping.
It is an obvious extension to make it a property of a jail
but I have not done so. It can be achieved by combining the setfib and
jail commands.
2/ packets received on an interface for forwarding.
By default these packets would use table 0,
(or possibly a number settable in a sysctl(not yet)).
but prior to routing the firewall can inspect them (see below).
(possibly in the future you may be able to associate a FIB
with packets received on an interface.. An ifconfig arg, but not yet.)
3/ packets inspected by a packet classifier, which can arbitrarily
associate a fib with it on a packet by packet basis.
A fib assigned to a packet by a packet classifier
(such as ipfw) would over-ride a fib associated by
a more default source. (such as cases 1 or 2).
4/ a tcp listen socket associated with a fib will generate
accept sockets that are associated with that same fib.
5/ Packets generated in response to some other packet (e.g. reset
or icmp packets). These should use the FIB associated with the
packet being reponded to.
6/ Packets generated during encapsulation.
gif, tun and other tunnel interfaces will encapsulate using the FIB
that was in effect withthe proces that set up the tunnel.
thus setfib 1 ifconfig gif0 [tunnel instructions]
will set the fib for the tunnel to use to be fib 1.
Routing messages would be associated with their
process, and thus select one FIB or another.
messages from the kernel would be associated with the fib they
refer to and would only be received by a routing socket associated
with that fib. (not yet implemented)
In addition Netstat has been edited to be able to cope with the
fact that the array is now 2 dimensional. (It looks in system
memory using libkvm (!)). Old versions of netstat see only the first FIB.
In addition two sysctls are added to give:
a) the number of FIBs compiled in (active)
b) the default FIB of the calling process.
Early testing experience:
-------------------------
Basically our (IronPort's) appliance does this functionality already
using ipfw fwd but that method has some drawbacks.
For example,
It can't fully simulate a routing table because it can't influence the
socket's choice of local address when a connect() is done.
Testing during the generating of these changes has been
remarkably smooth so far. Multiple tables have co-existed
with no notable side effects, and packets have been routes
accordingly.
ipfw has grown 2 new keywords:
setfib N ip from anay to any
count ip from any to any fib N
In pf there seems to be a requirement to be able to give symbolic names to the
fibs but I do not have that capacity. I am not sure if it is required.
SCTP has interestingly enough built in support for this, called VRFs
in Cisco parlance. it will be interesting to see how that handles it
when it suddenly actually does something.
Where to next:
--------------------
After committing the ABI compatible version and MFCing it, I'd
like to proceed in a forward direction in -current. this will
result in some roto-tilling in the routing code.
Firstly: the current code's idea of having a separate tree per
protocol family, all of the same format, and pointed to by the
1 dimensional array is a bit silly. Especially when one considers that
there is code that makes assumptions about every protocol having the
same internal structures there. Some protocols don't WANT that
sort of structure. (for example the whole idea of a netmask is foreign
to appletalk). This needs to be made opaque to the external code.
My suggested first change is to add routing method pointers to the
'domain' structure, along with information pointing the data.
instead of having an array of pointers to uniform structures,
there would be an array pointing to the 'domain' structures
for each protocol address domain (protocol family),
and the methods this reached would be called. The methods would have
an argument that gives FIB number, but the protocol would be free
to ignore it.
When the ABI can be changed it raises the possibilty of the
addition of a fib entry into the "struct route". Currently,
the structure contains the sockaddr of the desination, and the resulting
fib entry. To make this work fully, one could add a fib number
so that given an address and a fib, one can find the third element, the
fib entry.
Interaction with the ARP layer/ LL layer would need to be
revisited as well. Qing Li has been working on this already.
This work was sponsored by Ironport Systems/Cisco
PR:
Reviewed by: several including rwatson, bz and mlair (parts each)
Approved by:
Obtained from: Ironport systems/Cisco
MFC after:
Security:
PR:
Submitted by:
Reviewed by:
Approved by:
Obtained from:
MFC after:
Security:
486 lines
14 KiB
Groff
486 lines
14 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
|
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
|
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getsockopt.2 8.4 (Berkeley) 5/2/95
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.\" $FreeBSD$
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.\"
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.Dd March 8, 2007
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.Dt GETSOCKOPT 2
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.Os
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.Sh NAME
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.Nm getsockopt ,
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.Nm setsockopt
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.Nd get and set options on sockets
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.Ft int
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.Fn getsockopt "int s" "int level" "int optname" "void * restrict optval" "socklen_t * restrict optlen"
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.Ft int
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.Fn setsockopt "int s" "int level" "int optname" "const void *optval" "socklen_t optlen"
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.Sh DESCRIPTION
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The
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.Fn getsockopt
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and
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.Fn setsockopt
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system calls
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manipulate the
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.Em options
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associated with a socket.
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Options may exist at multiple
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protocol levels; they are always present at the uppermost
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.Dq socket
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level.
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.Pp
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When manipulating socket options the level at which the
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option resides and the name of the option must be specified.
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To manipulate options at the socket level,
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.Fa level
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is specified as
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.Dv SOL_SOCKET .
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To manipulate options at any
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other level the protocol number of the appropriate protocol
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controlling the option is supplied.
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For example,
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to indicate that an option is to be interpreted by the
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.Tn TCP
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protocol,
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.Fa level
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should be set to the protocol number of
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.Tn TCP ;
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see
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.Xr getprotoent 3 .
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.Pp
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The
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.Fa optval
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and
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.Fa optlen
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arguments
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are used to access option values for
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.Fn setsockopt .
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For
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.Fn getsockopt
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they identify a buffer in which the value for the
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requested option(s) are to be returned.
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For
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.Fn getsockopt ,
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.Fa optlen
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is a value-result argument, initially containing the
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size of the buffer pointed to by
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.Fa optval ,
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and modified on return to indicate the actual size of
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the value returned.
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If no option value is
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to be supplied or returned,
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.Fa optval
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may be NULL.
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.Pp
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The
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.Fa optname
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argument
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and any specified options are passed uninterpreted to the appropriate
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protocol module for interpretation.
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The include file
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.In sys/socket.h
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contains definitions for
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socket level options, described below.
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Options at other protocol levels vary in format and
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name; consult the appropriate entries in
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section
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4 of the manual.
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.Pp
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Most socket-level options utilize an
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.Vt int
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argument for
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.Fa optval .
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For
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.Fn setsockopt ,
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the argument should be non-zero to enable a boolean option,
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or zero if the option is to be disabled.
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.Dv SO_LINGER
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uses a
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.Vt "struct linger"
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|
argument, defined in
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.In sys/socket.h ,
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|
which specifies the desired state of the option and the
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linger interval (see below).
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|
.Dv SO_SNDTIMEO
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and
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.Dv SO_RCVTIMEO
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|
use a
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.Vt "struct timeval"
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argument, defined in
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.In sys/time.h .
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.Pp
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|
The following options are recognized at the socket level.
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Except as noted, each may be examined with
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.Fn getsockopt
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and set with
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.Fn setsockopt .
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.Bl -column SO_ACCEPTFILTER -offset indent
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.It Dv SO_DEBUG Ta "enables recording of debugging information"
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.It Dv SO_REUSEADDR Ta "enables local address reuse"
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.It Dv SO_REUSEPORT Ta "enables duplicate address and port bindings"
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.It Dv SO_KEEPALIVE Ta "enables keep connections alive"
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.It Dv SO_DONTROUTE Ta "enables routing bypass for outgoing messages"
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.It Dv SO_LINGER Ta "linger on close if data present"
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.It Dv SO_BROADCAST Ta "enables permission to transmit broadcast messages"
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.It Dv SO_OOBINLINE Ta "enables reception of out-of-band data in band"
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.It Dv SO_SNDBUF Ta "set buffer size for output"
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.It Dv SO_RCVBUF Ta "set buffer size for input"
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.It Dv SO_SNDLOWAT Ta "set minimum count for output"
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.It Dv SO_RCVLOWAT Ta "set minimum count for input"
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.It Dv SO_SNDTIMEO Ta "set timeout value for output"
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.It Dv SO_RCVTIMEO Ta "set timeout value for input"
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.It Dv SO_ACCEPTFILTER Ta "set accept filter on listening socket"
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.It Dv SO_NOSIGPIPE Ta
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controls generation of
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.Dv SIGPIPE
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for the socket
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.It Dv SO_TIMESTAMP Ta "enables reception of a timestamp with datagrams"
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.It Dv SO_BINTIME Ta "enables reception of a timestamp with datagrams"
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.It Dv SO_ACCEPTCONN Ta "get listening status of the socket (get only)"
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.It Dv SO_TYPE Ta "get the type of the socket (get only)"
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.It Dv SO_ERROR Ta "get and clear error on the socket (get only)"
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.It Dv SO_SETFIB Ta "set the associated FIB (routing table) for the socket (set only)"
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.El
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.Pp
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.Dv SO_DEBUG
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enables debugging in the underlying protocol modules.
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.Dv SO_REUSEADDR
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indicates that the rules used in validating addresses supplied
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in a
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.Xr bind 2
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system call should allow reuse of local addresses.
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.Dv SO_REUSEPORT
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allows completely duplicate bindings by multiple processes
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if they all set
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.Dv SO_REUSEPORT
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before binding the port.
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This option permits multiple instances of a program to each
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receive UDP/IP multicast or broadcast datagrams destined for the bound port.
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.Dv SO_KEEPALIVE
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enables the
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periodic transmission of messages on a connected socket.
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Should the
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connected party fail to respond to these messages, the connection is
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considered broken and processes using the socket are notified via a
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.Dv SIGPIPE
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signal when attempting to send data.
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.Dv SO_DONTROUTE
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indicates that outgoing messages should
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bypass the standard routing facilities.
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Instead, messages are directed
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to the appropriate network interface according to the network portion
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of the destination address.
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.Pp
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.Dv SO_LINGER
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controls the action taken when unsent messages
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are queued on socket and a
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.Xr close 2
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is performed.
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If the socket promises reliable delivery of data and
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.Dv SO_LINGER
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is set,
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the system will block the process on the
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.Xr close 2
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attempt until it is able to transmit the data or until it decides it
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is unable to deliver the information (a timeout period, termed the
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linger interval, is specified in seconds in the
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.Fn setsockopt
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system call when
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.Dv SO_LINGER
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is requested).
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If
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.Dv SO_LINGER
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is disabled and a
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.Xr close 2
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is issued, the system will process the close in a manner that allows
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the process to continue as quickly as possible.
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.Pp
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The option
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.Dv SO_BROADCAST
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requests permission to send broadcast datagrams
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on the socket.
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Broadcast was a privileged operation in earlier versions of the system.
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With protocols that support out-of-band data, the
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.Dv SO_OOBINLINE
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option
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requests that out-of-band data be placed in the normal data input queue
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as received; it will then be accessible with
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.Xr recv 2
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or
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.Xr read 2
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calls without the
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.Dv MSG_OOB
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flag.
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Some protocols always behave as if this option is set.
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.Dv SO_SNDBUF
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and
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.Dv SO_RCVBUF
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are options to adjust the normal
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buffer sizes allocated for output and input buffers, respectively.
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The buffer size may be increased for high-volume connections,
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or may be decreased to limit the possible backlog of incoming data.
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|
The system places an absolute maximum on these values, which is accessible
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through the
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.Xr sysctl 3
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MIB variable
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.Dq Li kern.ipc.maxsockbuf .
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.Pp
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.Dv SO_SNDLOWAT
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is an option to set the minimum count for output operations.
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Most output operations process all of the data supplied
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by the call, delivering data to the protocol for transmission
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and blocking as necessary for flow control.
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Nonblocking output operations will process as much data as permitted
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subject to flow control without blocking, but will process no data
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if flow control does not allow the smaller of the low water mark value
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or the entire request to be processed.
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A
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.Xr select 2
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operation testing the ability to write to a socket will return true
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only if the low water mark amount could be processed.
|
|
The default value for
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.Dv SO_SNDLOWAT
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is set to a convenient size for network efficiency, often 1024.
|
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.Dv SO_RCVLOWAT
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is an option to set the minimum count for input operations.
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In general, receive calls will block until any (non-zero) amount of data
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is received, then return with the smaller of the amount available or the amount
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requested.
|
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The default value for
|
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.Dv SO_RCVLOWAT
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is 1.
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If
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.Dv SO_RCVLOWAT
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is set to a larger value, blocking receive calls normally
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wait until they have received the smaller of the low water mark value
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or the requested amount.
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Receive calls may still return less than the low water mark if an error
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occurs, a signal is caught, or the type of data next in the receive queue
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is different from that which was returned.
|
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.Pp
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.Dv SO_SNDTIMEO
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is an option to set a timeout value for output operations.
|
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It accepts a
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.Vt "struct timeval"
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argument with the number of seconds and microseconds
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used to limit waits for output operations to complete.
|
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If a send operation has blocked for this much time,
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it returns with a partial count
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or with the error
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.Er EWOULDBLOCK
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if no data were sent.
|
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In the current implementation, this timer is restarted each time additional
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data are delivered to the protocol,
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implying that the limit applies to output portions ranging in size
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from the low water mark to the high water mark for output.
|
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.Dv SO_RCVTIMEO
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is an option to set a timeout value for input operations.
|
|
It accepts a
|
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.Vt "struct timeval"
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argument with the number of seconds and microseconds
|
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used to limit waits for input operations to complete.
|
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In the current implementation, this timer is restarted each time additional
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data are received by the protocol,
|
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and thus the limit is in effect an inactivity timer.
|
|
If a receive operation has been blocked for this much time without
|
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receiving additional data, it returns with a short count
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or with the error
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.Er EWOULDBLOCK
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|
if no data were received.
|
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.Pp
|
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.Dv SO_SETFIB
|
|
can be used to over-ride the default FIB (routing table) for the given socket.
|
|
The value must be from 0 to one less than the number returned from
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the sysctl
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.Em net.fibs .
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.Pp
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.Dv SO_ACCEPTFILTER
|
|
places an
|
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.Xr accept_filter 9
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|
on the socket,
|
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which will filter incoming connections
|
|
on a listening stream socket before being presented for
|
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.Xr accept 2 .
|
|
Once more,
|
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.Xr listen 2
|
|
must be called on the socket before
|
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trying to install the filter on it,
|
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or else the
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.Fn setsockopt
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|
system call will fail.
|
|
.Bd -literal
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|
struct accept_filter_arg {
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|
char af_name[16];
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|
char af_arg[256-16];
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|
};
|
|
.Ed
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|
.Pp
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|
The
|
|
.Fa optval
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|
argument
|
|
should point to a
|
|
.Fa struct accept_filter_arg
|
|
that will select and configure the
|
|
.Xr accept_filter 9 .
|
|
The
|
|
.Fa af_name
|
|
argument
|
|
should be filled with the name of the accept filter
|
|
that the application wishes to place on the listening socket.
|
|
The optional argument
|
|
.Fa af_arg
|
|
can be passed to the accept
|
|
filter specified by
|
|
.Fa af_name
|
|
to provide additional configuration options at attach time.
|
|
Passing in an
|
|
.Fa optval
|
|
of NULL will remove the filter.
|
|
.Pp
|
|
The
|
|
.Dv SO_NOSIGPIPE
|
|
option controls generation of the
|
|
.Dv SIGPIPE
|
|
signal normally sent
|
|
when writing to a connected socket where the other end has been
|
|
closed returns with the error
|
|
.Er EPIPE .
|
|
.Pp
|
|
If the
|
|
.Dv SO_TIMESTAMP
|
|
or
|
|
.Dv SO_BINTIME
|
|
option is enabled on a
|
|
.Dv SOCK_DGRAM
|
|
socket, the
|
|
.Xr recvmsg 2
|
|
call will return a timestamp corresponding to when the datagram was received.
|
|
The
|
|
.Va msg_control
|
|
field in the
|
|
.Vt msghdr
|
|
structure points to a buffer that contains a
|
|
.Vt cmsghdr
|
|
structure followed by a
|
|
.Vt "struct timeval"
|
|
for
|
|
.Dv SO_TIMESTAMP
|
|
and
|
|
.Vt "struct bintime"
|
|
for
|
|
.Dv SO_BINTIME .
|
|
The
|
|
.Vt cmsghdr
|
|
fields have the following values for TIMESTAMP:
|
|
.Bd -literal
|
|
cmsg_len = sizeof(struct timeval);
|
|
cmsg_level = SOL_SOCKET;
|
|
cmsg_type = SCM_TIMESTAMP;
|
|
.Ed
|
|
.Pp
|
|
and for
|
|
.Dv SO_BINTIME :
|
|
.Bd -literal
|
|
cmsg_len = sizeof(struct bintime);
|
|
cmsg_level = SOL_SOCKET;
|
|
cmsg_type = SCM_BINTIME;
|
|
.Ed
|
|
.Pp
|
|
Finally,
|
|
.Dv SO_ACCEPTCONN ,
|
|
.Dv SO_TYPE
|
|
and
|
|
.Dv SO_ERROR
|
|
are options used only with
|
|
.Fn getsockopt .
|
|
.Dv SO_ACCEPTCONN
|
|
returns whether the socket is currently accepting connections,
|
|
that is, whether or not the
|
|
.Xr listen 2
|
|
system call was invoked on the socket.
|
|
.Dv SO_TYPE
|
|
returns the type of the socket, such as
|
|
.Dv SOCK_STREAM ;
|
|
it is useful for servers that inherit sockets on startup.
|
|
.Dv SO_ERROR
|
|
returns any pending error on the socket and clears
|
|
the error status.
|
|
It may be used to check for asynchronous errors on connected
|
|
datagram sockets or for other asynchronous errors.
|
|
.Sh RETURN VALUES
|
|
.Rv -std
|
|
.Sh ERRORS
|
|
The call succeeds unless:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EBADF
|
|
The argument
|
|
.Fa s
|
|
is not a valid descriptor.
|
|
.It Bq Er ENOTSOCK
|
|
The argument
|
|
.Fa s
|
|
is a file, not a socket.
|
|
.It Bq Er ENOPROTOOPT
|
|
The option is unknown at the level indicated.
|
|
.It Bq Er EFAULT
|
|
The address pointed to by
|
|
.Fa optval
|
|
is not in a valid part of the process address space.
|
|
For
|
|
.Fn getsockopt ,
|
|
this error may also be returned if
|
|
.Fa optlen
|
|
is not in a valid part of the process address space.
|
|
.It Bq Er EINVAL
|
|
Installing an
|
|
.Xr accept_filter 9
|
|
on a non-listening socket was attempted.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr ioctl 2 ,
|
|
.Xr listen 2 ,
|
|
.Xr recvmsg 2 ,
|
|
.Xr socket 2 ,
|
|
.Xr getprotoent 3 ,
|
|
.Xr sysctl 3 ,
|
|
.Xr protocols 5 ,
|
|
.Xr sysctl 8 ,
|
|
.Xr accept_filter 9 ,
|
|
.Xr bintime 9
|
|
.Sh HISTORY
|
|
The
|
|
.Fn getsockopt
|
|
system call appeared in
|
|
.Bx 4.2 .
|
|
.Sh BUGS
|
|
Several of the socket options should be handled at lower levels of the system.
|