IPSEC_SET_POLICY(3) | Library Functions Manual | IPSEC_SET_POLICY(3) |
ipsec_set_policy
,
ipsec_get_policylen
,
ipsec_dump_policy
—
#include <netipsec/ipsec.h>
char *
ipsec_set_policy
(const
char *policy, int
len);
int
ipsec_get_policylen
(char
*buf);
char *
ipsec_dump_policy
(char
*buf, const char
*delim);
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 structure.
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-readable 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 allocated string. It is the caller's responsibility
to free(3) it.
policy is formatted as either of the following:
discard
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:
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.
entrust
entrust
means to consult the SPD defined by
setkey(8).bypass
bypass
means to bypass the IPsec processing. (the packet will be transmitted in
clear). This is for privileged sockets.ipsec
request
...ipsec
means that the matching packets are subject to IPsec processing.
ipsec
can be followed by one or more
request strings, which are formatted as below:
/
mode /
src -
dst [/level]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 transmitted 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 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 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. However, 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
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.
January 4, 2012 | NetBSD 9.2 |