1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
|
# Copyright (c) 2007-2008 Roy Marples <roy@marples.name>
# Released under the 2-clause BSD license.
apipa_depend()
{
program /sbin/arping /bin/arping
}
_random_bytes_as_int()
{
local hex num_bytes="$1"
# While POSIX does not require that /dev/urandom exist, it is a
# de-facto standard. Therefore, the following approach should be
# highly portable in practice. In the case of Linux, and unlike BSD
# this interface does not block in the event that the CSRNG has not
# yet been seeded. Still, this is acceptable because we do not
# require a guarantee that the entropy be cryptographically secure.
# It's also worth noting that Linux >=5.4 is faster at seeding in
# the absence of RDRAND/RDSEED than previous versions were.
test -e /dev/urandom &&
hex=$(
LC_ALL=C tr -dc '[:xdigit:]' < /dev/urandom |
dd bs="$(( num_bytes * 2 ))" count=1 2>/dev/null) &&
test "${#hex}" = "$(( num_bytes * 2 ))" &&
printf '%d\n' "0x${hex}"
}
_random_apipa_octets()
{
local seed
# Obtain a highly random 16-bit seed for use by awk's RNG. In the
# unlikely event that the seed ends up being empty, awk will seed
# based on the time of day, with a granularity of one second.
seed=$(_random_bytes_as_int 2)
# For APIPA (RFC 3927), the 169.254.0.0/16 address block is
# reserved. This provides 65024 addresses, having accounted for the
# fact that the first and last /24 are reserved for future use.
awk "BEGIN {
srand($seed)
for (i=256; i<65280; i++) print rand() \" \" i
}" |
sort -k 1,1 -n |
POSIXLY_CORRECT=1 awk '{
hex = sprintf("%04x",$2)
printf("%d %d\n", "0x" substr(hex,1,2), "0x" substr(hex,3,2))
}'
}
apipa_start()
{
local addr rc
_exists || return
einfo "Searching for free addresses in 169.254.0.0/16"
eindent
exec 3>&1
addr=$(
_random_apipa_octets |
{
while read -r i1 i2; do
addr="169.254.${i1}.${i2}"
vebegin "${addr}/16" >&3
if ! arping_address "${addr}" >&3; then
printf '%s\n' "${addr}"
exit 0
fi
done
exit 1
}
)
rc=$?
exec 3>&-
if [ "$rc" = 0 ]; then
eval "config_${config_index}=\"\${addr}/16 broadcast 169.254.255.255\""
: $(( config_index -= 1 ))
veend 0
else
eerror "No free address found!"
fi
eoutdent
return "$rc"
}
|
GitWeb