ipsec_set_policy(3) BSD Library Functions Manual ipsec_set_policy(3)

NAME

 ipsec_dump_policy, ipsec_get_policylen, ipsec_set_policy -- manipulate
 IPsec policy specification structure from human-readable policy string

LIBRARY

 IPsec Policy Control Library (libipsec, -lipsec)

SYNOPSIS

 #include <netinet6/ipsec.h>
 char *
 ipsec_dump_policy(caddr_t buf, char *delim);
 int
 ipsec_get_policylen(caddr_t buf);
 char *
 ipsec_set_policy(char *policy, int len);

DESCRIPTION

 ipsec_set_policy() generates an IPsec policy specification structure,
 namely 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 policy and its length len. ipsec_set_policy() will
 return a buffer with the corresponding IPsec policy specification struc-
 ture. The buffer is dynamically allocated, and must be free(3) 'd by the
 caller.
 You can get the length of the generated buffer with ipsec_get_policylen()
 (i.e. for calling setsockopt(2) ).
 ipsec_dump_policy() converts an IPsec policy structure into human-read-
 able form. Therefore, ipsec_dump_policy() can be regarded as the inverse
 function to ipsec_set_policy(). buf points to an IPsec policy structure,
 struct sadb_x_policy. delim is a delimiter string, which is usually a
 blank character. If you set delim to NULL, a single whitespace is
 assumed. ipsec_dump_policy() returns a pointer to a dynamically allo-
 cated string. It is the caller's responsibility to free(3)  it.
 policy is formatted as either of the following:
 direction [priority specification] discard
 direction must be in, out, or fwd. direction specifies in which
 direction the policy needs to be applied. The non-standard
 direction fwd is substituted with in on platforms which do not
 support forward policies.
 priority specification is used to control the placement of the
 policy within the SPD. The policy position is determined by a
 signed integer where higher priorities indicate the policy is
 placed closer to the beginning of the list and lower priorities
 indicate the policy is placed closer to the end of the list.
 Policies with equal priorities are added at the end of the group
 of such policies.
 Priority can only be specified when libipsec has been compiled
 against kernel headers that support policy priorities (Linux >=
 2.6.6). It takes one of the following formats:
 {priority,prio} offset
 offset is an integer in the range
 -2147483647..214783648.
 {priority,prio} base {+,-} offset
 base is either low (-1073741824), def (0), or high
 (1073741824).
 offset is an unsigned integer. It can be up to
 1073741824 for positive offsets, and up to 1073741823
 for negative offsets.
 The interpretation of policy priority in these functions and the
 kernel DOES differ. The relationship between the two can be
 described as p(kernel) = 0x80000000 - p(func)
 With discard policy, packets will be dropped if they match the
 policy.
 direction [priority specification] entrust
 entrust means to consult the SPD defined by setkey(8) .
 direction [priority specification] bypass
 bypass means to bypass the IPsec processing. (the packet will
 be transmitted in clear). This is for privileged sockets.
 direction [priority specification] ipsec request ...
 ipsec means that the matching packets are subject to IPsec pro-
 cessing. ipsec can be followed by one or more request strings,
 which are formatted as below:
 protocol / mode / src - dst [/level]
 protocol is either ah, esp, or ipcomp.
 mode is either transport or tunnel.
 src and dst specifies the IPsec endpoint. src always
 means the ``sending node'' and dst always means the
 ``receiving node''. Therefore, when direction is in,
 dst is this node and src is the other node (peer). If
 mode is transport, Both src and dst can be omitted.
 level must be set to one of the following: default,
 use, require, or unique. default means that the kernel
 should consult the system default policy defined by
 sysctl(8) , such as net.inet.ipsec.esp_trans_deflev.
 See ipsec(4)  regarding the system default. 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 transmit-
 ted in clear (when SA is not available), or encrypted
 (when SA is available). require means that a relevant
 SA is required, since the kernel must perform IPsec
 operation against packets. unique is the same as
 require, but adds the restriction that the SA for out-
 bound 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
 unique like unique: number. number must be between 1
 and 32767 . If the request string is kept unambiguous,
 level and slash prior to level can be omitted. How-
 ever, it is encouraged to specify them explicitly to
 avoid unintended behavior. If level is omitted, it
 will be interpreted as default.
 Note that there are slight differences to the specification of
 setkey(8) . In the specification of setkey(8) , both entrust and
 bypass are not used. Refer to setkey(8)  for details.
 Here are several examples (long lines are wrapped for
 readability):
 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

RETURN VALUES

 ipsec_set_policy() returns a pointer to the allocated buffer with the
 policy specification if successful; otherwise a NULL pointer is returned.
 ipsec_get_policylen() returns a positive value (meaning the buffer size)
 on success, and a negative value on errors. ipsec_dump_policy() returns
 a pointer to a dynamically allocated region on success, and NULL on
 errors.

SEE ALSO

 ipsec_strerror(3) , ipsec(4) , setkey(8) 

HISTORY

 The functions first appeared in the WIDE/KAME IPv6 protocol stack kit.
BSD May 5, 1998 BSD