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.Dd May 5, 1998
.Dt IPSEC_SET_POLICY 3
.Os
.Sh NAME
.Nm ipsec_set_policy ,
.Nm ipsec_get_policylen ,
.Nm ipsec_dump_policy
.Nd manipulate IPsec policy specification structure from readable string
.\"
.Sh LIBRARY
.Lb libipsec
.Sh SYNOPSIS
.Fd #include <netinet6/ipsec.h>
.Ft "char *"
.Fn ipsec_set_policy "char *policy" "int len"
.Ft int
.Fn ipsec_get_policylen "char *buf"
.Ft "char *"
.Fn ipsec_dump_policy "char *buf" "char *delim"
.Sh DESCRIPTION
.Fn ipsec_set_policy
generates IPsec policy specification structure, namely
.Li struct sadb_x_policy
and/or
.Li struct sadb_x_ipsecrequest
from human-readable policy specification.
policy specification must be given as C string
.Fa policy
and length
.Fa len
of
.Fa policy .
.Fn ipsec_set_policy
will return the buffer of IPsec policy specification structure.
.Pp
You may want the length of the generated buffer such when calling
.Xr setsockopt 2 .
.Fn ipsec_get_policylen
will return the length.
.Pp
.Fn ipsec_dump_policy
converts IPsec policy structure into readable form.
Therefore,
.Fn ipsec_dump_policy
can be regarded as inverse conversion of
.Fn ipsec_set_policy .
.Fa buf
points to a IPsec policy structure,
.Li struct sadb_x_policy .
.Fa delim
is a delimiter string, which is usually a blank character.
If you set
.Fa delim
to
.Dv NULL ,
single whitespace is assumed.
.Fn ipsec_dump_policy
returns pointer to dynamically allocated string.
It is caller's responsibility to reclaim the region, by using
.Xr free 3 .
.Pp
.Fa policy
is formatted as either of the following:
.Bl -tag  -width "discard"
.It Ar direction Li discard
.Ar direction
must be
.Li in
or
.Li out .
.Ar direction
specifies which direction the policy needs to be applied.
With
.Li discard
policy, packets will be dropped if they match the policy.
.It Ar direction Li entrust
.Li entrust
means to consult to SPD defined by
.Xr setkey 8 .
.It Ar direction Li bypass
.Li bypass
means to be bypassed the IPsec processing.
.Pq packet will be transmitted in clear .
This is for privileged socket.
.It Xo
.Ar direction
.Li ipsec
.Ar request ...
.Xc
.Li ipsec
means that the matching packets are subject to IPsec processing.
.Li ipsec
can be followed by one or more
.Ar request
string, which is formatted as below:
.Bl -tag  -width "discard"
.It Xo
.Ar protocol
.Li /
.Ar mode
.Li /
.Ar src
.Li -
.Ar dst
.Op Ar /level
.Xc
.Ar protocol
is either
.Li ah ,
.Li esp
or
.Li ipcomp .
.Pp
.Ar mode
is either
.Li transport
or
.Li tunnel .
.Pp
.Ar src
and
.Ar dst
specifies IPsec endpoint.
.Ar src
always means
.Dq sending node
and
.Ar dst
always means
.Dq receiving node .
Therefore, when
.Ar direction
is
.Li in ,
.Ar dst
is this node
and
.Ar src
is the other node
.Pq peer .
If
.Ar mode
is
.Li transport ,
Both
.Ar src
and
.Ar dst
can be omited. 
.Pp
.Ar level
must be set to one of the following:
.Li default , use , require
or
.Li unique .
.Li default
means that the kernel should consult the system default policy
defined by
.Xr sysctl 8 ,
such as
.Li net.inet.ipsec.esp_trans_deflev .
See
.Xr ipsec 4
regarding the system default.
.Li use
means that a relevant SA can be used when available,
since the kernel may perform IPsec operation against packets when possible.
In this case, packets can be transmitted in clear
.Pq when SA is not available ,
or encrypted
.Pq when SA is available .
.Li require
means that a relevant SA is required,
since the kernel must perform IPsec operation against packets.
.Li unique
is the same as
.Li require ,
but adds the restriction that the SA for outbound traffic is used
only for this policy.
You may need the identifier in order to relate the policy and the SA
when you define the SA by manual keying.
You can put the decimal number as the identifier after
.Li unique
like
.Li unique : number .
.Li number
must be between 1 and 32767 .
If the
.Ar request
string is kept unambiguous,
.Ar level
and slash prior to
.Ar level
can be omitted.
However, it is encouraged to specify them explicitly
to avoid unintended behaviors.
If
.Ar level
is omitted, it will be interpreted as
.Li default .
.El
.El
.Pp
Note that there is a bit difference of specification from
.Xr setkey 8 .
In specification by
.Xr setkey 8 ,
both entrust and bypass are not used.
Refer to
.Xr setkey 8
for detail.
.Pp
Here are several examples
.Pq long lines are wrapped for readability :
.Bd -literal -offset indent
in discard
out ipsec esp/transport//require
in ipsec ah/transport//require
out ipsec esp/tunnel/10.1.1.2-10.1.1.1/use
in ipsec ipcomp/transport//use
        esp/transport//use
.Ed
.Sh RETURN VALUES
.Fn ipsec_set_policy
returns a pointer to the allocated buffer of policy specification if successful; otherwise a NULL pointer is returned.
.Fn ipsec_get_policylen
returns with positive value
.Pq meaning the buffer size
on success, and negative value on errors.
.Fn ipsec_dump_policy
returns a pointer to dynamically allocated region on success,
and
.Dv NULL
on errors.
.Sh SEE ALSO
.Xr ipsec_strerror 3 ,
.Xr ipsec 4 ,
.Xr setkey 8
.Sh HISTORY
The functions first appeared in WIDE/KAME IPv6 protocol stack kit.
.Pp
IPv6 and IPsec support based on the KAME Project (http://www.kame.net/) stack
was initially integrated into
.Fx 4.0