URL: <https://savannah.gnu.org/bugs/?65940>
Summary: Add netmask and dns IP address variables for use in
grub
Group: GNU GRUB
Submitter: papamoose
Submitted: Wed 03 Jul 2024 01:41:41 AM UTC
Category: User Interface
Severity: Major
Priority: 5 - Normal
Item Group: Feature Request
Status: None
Privacy: Public
Assigned to: None
Originator Name:
Originator Email:
Open/Closed: Open
Release: other
Release:
Discussion Lock: Any
Reproducibility: Every Time
Planned Release: None
_______________________________________________________
Follow-up Comments:
-------------------------------------------------------
Date: Wed 03 Jul 2024 01:41:41 AM UTC By: Phil <papamoose>
I download grubnetx64.efi.signed and shimx64.efi.dualsigned from Ubuntu to use
for pxe booting grub and provide a menu.
Specifically Ubuntu 22.04 for this example.
* shim-signed 1.51.3+15.7-0ubuntu1
* grub-efi-amd64-signed 1.187.6+2.06-2ubuntu14.4
```
apt download grub-efi-amd64-signed
dpkg-deb --fsys-tarfile grub-efi-amd64-signed*deb | tar x
./usr/lib/grub/x86_64-efi-signed/grubnetx64.efi.signed -O >
${wdir}/grubx64.efi
```
In the menu I display the IP address the machine received from the dhcp server
and use elsewhere on the kernel command line on other menu entries.
There are a few builtin variables that are useful for this: net_default_mac,
net_default_ip, net_default_server.
However, there is no option to get the netmask and dns server.
Example usage in the menu:
menuentry "MAC: ${net_default_mac}" { true }
menuentry "IP: ${net_default_ip}" { true }
menuentry "GATEWAY: ${net_default_server}" { true }
menuentry "NETMASK: ${netmask}" { true }
menuentry "DNS: ${dns}" { true }
menuentry "ARCH: ${arch}" { true }
I have resorted to writing the following function inside grub.cfg to grab
decode hexidecimal you get from net_get_dhcp_option() and save it to a
variable.
```
function hex2ip4 {
set hex=$1
regexp --set mask_octet1 (..)...... $hex
regexp --set mask_octet2 ..(..).... $hex
regexp --set mask_octet3 ....(..).. $hex
regexp --set mask_octet4 ......(..) $hex
set nm=""
for hexguess in $mask_octet1 $mask_octet2 $mask_octet3 $mask_octet4; do
for i in 255 254 253 252 251 250 249 248 247 246 245 244 243 242 241 240
239 238 237 236 235 234 233 232 231 230 229 228 227 226 225 224 223 222 221
220 219 218 217 216 215 214 213 212 211 210 209 208 207 206 205 204 203 202
201 200 199 198 197 196 195 194 193 192 191 190 189 188 187 186 185 184 183
182 181 180 179 178 177 176 175 174 173 172 171 170 169 168 167 166 165 164
163 162 161 160 159 158 157 156 155 154 153 152 151 150 149 148 147 146 145
144 143 142 141 140 139 138 137 136 135 134 133 132 131 130 129 128 127 126
125 124 123 122 121 120 119 118 117 116 115 114 113 112 111 110 109 108 107
106 105 104 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83
82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57
56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31
30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2
1 0; do
if [ 0x$hexguess -eq $i ]; then
set nm="${nm}${i}."
continue
fi
done
done
regexp --set $2 (.*). $nm
}
net_get_dhcp_option netmask_hex $net_default_interface 1 hex
hex2ip4 $netmask_hex netmask
net_get_dhcp_option dns_hex $net_default_interface 6 hex
hex2ip4 $dns_hex dns
```
A. Is there new functionality that provides this information now?
B. Can the netmask and dns server ips be provided under net_default_ or
elsewhere?
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