IPSEC_SET_POLICY(3) BSD Library Functions Manual IPSEC_SET_POLICY(3)NAME
ipsec_set_policy, ipsec_get_policylen, ipsec_dump_policy — create an
IPsec policy structure from a human readable string
IPsec Policy Control Library (libipsec, -lipsec)
ipsec_set_policy(char *policy, int len);
ipsec_dump_policy(char *buf, char *delim);
The ipsec_set_policy() function generates an IPsec policy specification
structure, struct sadb_x_policy and/or struct sadb_x_ipsecrequest from a
human-readable policy specification. The policy specification must be
given as a C string, passed in the policy argument and the length of the
string, given as len. The ipsec_set_policy() function returns pointer to
a buffer which contains a properly formed IPsec policy specification
structure. The buffer is dynamically allocated, and must be freed by
using the free(3) library function.
The ipsec_get_policylen() function will returns the of the buffer which
is needed when passing the specification structure to the setsockopt(2)
The ipsec_dump_policy() function converts an IPsec policy structure into
a human readable form. The buf argument points to an IPsec policy struc‐
ture, struct sadb_x_policy. delim is a delimiter string, which is usu‐
ally a blank character. If you set delim to NULL, a single white space
is assumed. The ipsec_dump_policy() function returns a pointer to dynam‐
ically allocated string. It is the caller's responsibility to free the
returned pointer using the free(3) library call.
A policy is given in the following way:
The direction must be in or out and specifies which direction
the policy needs to be applied, either on inbound or outbound
packets. When the discard policy is selected, packets will be
dropped if they match the policy.
entrust means to consult the security policy database (SPD) in
the kernel, as controlled by setkey(8).
A direction of bypass indicates that IPsec processing should not
occur and that the packet will be transmitted in clear. The
bypass option is only available to privileged sockets.
direction ipsec request ...
A direction of ipsec means that matching packets are processed
by IPsec. ipsec can be followed by one or more request string,
which is formatted as:
protocol / mode / src - dst [/level]
The protocol is one of: ah, esp or ipcomp indicating
Authentication Header, Encapsulating Security Protocol
or IP Compression protocol is used.
The mode is either transport or tunnel the meanings of
both modes are described in ipsec(4).
The src and dst specify the IP address, either v4 or
v6, of the source and destination systems. The src
always stands for the “sending node” and dst always
stands for the “receiving node”. When direction is in,
dst is this local node and src is the remote node or
peer. If mode is transport, both src and dst can be
The level must be set to one of the following: default,
use, require or unique. default means that the kernel
should consult the default security policies as defined
by a set of sysctl(8), variables. The relevant
sysctl(8) variables are described in ipsec(4).
When use is selected a relevant security association
(SA) can be used when available but is not necessary.
If the SA is available then packets will be handled by
IPsec, i.e., encrypted and/or authenticated but if an
SA is not available then packets will be transmitted in
the clear. The use option is not recommended because
it allows for accidental mis-configurations where
encrypted or authenticated link becomes unencrypted or
unauthenticated, the require keyword is recommended
instead of use where possible. Using the require key‐
word means that a relevant SA is required, and that the
kernel must perform IPsec processing on all matching
The unique keyword has the same effect as require, but
adds the restriction that the SA for outbound traffic
is used only for this policy. You may need the identi‐
fier in order to relate the policy and the SA when you
define the SA by manual keying using setkey(8). Put
the decimal number as the identifier after the unique
keyword in this way: unique: number, where number must
be between 1 and 32767.
If the request string is kept unambiguous, level and
the slash prior to level can be omitted but you are
encouraged to specify them explicitly to avoid unin‐
tended behaviors. If level is omitted, it will be
interpreted as default.
Note that there is a difference between the specification allowed here
and in setkey(8). When specifying security policies with setkey(8), nei‐
ther entrust nor bypass are used. Refer to setkey(8) for details.
The ipsec_set_policy() function returns a pointer to the allocated buffer
containing a the policy specification if successful; otherwise a NULL
pointer is returned.
The ipsec_get_policylen() function returns a positive value, indicating
the buffer size, on success, and a negative value on error.
The ipsec_dump_policy() function returns a pointer to a dynamically allo‐
cated region containing a human readable security policy on success, and
NULL on error.
Set a policy that all inbound packets are discarded.
All outbound packets are required to be processed by IPsec and trans‐
ported using ESP.
out ipsec esp/transport//require
All inbound packets are required to be authenticated using the AH proto‐
in ipsec ah/transport//require
Tunnel packets outbound through the endpoints at 10.1.1.2 and 10.1.1.1.
out ipsec esp/tunnel/10.1.1.2-10.1.1.1/require
SEE ALSOipsec_strerror(3), ipsec(4), setkey(8)HISTORY
These functions first appeared in WIDE/KAME IPv6 protocol stack kit.
IPv6 and IPsec support based on the KAME Project (http://www.kame.net/)
stack was initially integrated into FreeBSD 4.0.
BSD February 14, 2006 BSD