[Dnsmasq-discuss] Option 12 hostname sent to RPi seems incorrect
Geert Stappers
stappers at stappers.nl
Wed Oct 20 20:56:02 UTC 2021
On Wed, Oct 20, 2021 at 02:48:27PM +0530, Shrenik Bhura wrote:
> On Wed, 20 Oct, 2021, 11:21 Geert Stappers wrote:
> > On Wed, Oct 20, 2021 at 07:50:58AM +0530, Shrenik Bhura wrote:
> > >
> > > Hi Dominik,
> >
> > Hello Archive visitor,
> > Hello Mailinglist subscriber,
> >
> >
> > > There isn't anything specific in the configuration that serves the
> > > hostname. I am aware of this feature and when defined it works as desired.
> > > But when nothing is explicitly defined to serve hostnames, it is defaulting
> > > to 192 as visible in the logs, and only in the case of an RPi.
> > > When checked on the client with the hostname command, it shows the full
> > > hostname - 192.168.67.53
> >
> > Such hostname do I call IPaddress.
> >
> >
> > > The same configuration works fine with a x86 system as no hostname is being
> > > served when none is defined.
> > >
> > > Also it would be ideal to improve the logs as well to reflect the full
> > > hostname, if at all.
> > >
> > > Have attached the config files involved.
> >
> > Make a packet capture and put the .pcap on a server.
> > Then tell here how to fetch the file.
> > Next can those who care examine the .pcap with their tool.
> > (wireshark / tcpdump)
> >
> > > Once again, do note that this is the case only for an RPi. So there is some
> > > specific logic in dnsmasq coming into play for an RPi that seems to be
> > > serving the IP address as the default hostname when none is present.
> >
> > So beside the
> > /sbin/tcpdump -w rpi.pcap ether host dc:a6:32:78:98:ae
> > also
> > /sbin/tcpdump -w worksfine.pcap ether host MAC_address_of_known_good
> >
>
> Herein is the link to the related packet captures of an RPi and x86 system
> -
> https://drive.google.com/file/d/11RwpCdbE8W0ohS2QDj4BarZ_VHnEhwfs/view?usp=sharing
>
The "works fine" is/was captured different as the Raspi capture.
Luckly is the Raspi packet capture the better one, it contains replies.
|$ tcpdump -r worksfine.pcap port bootpc
|reading from file worksfine.pcap, link-type EN10MB (Ethernet), snapshot length 262144
|10:52:34.037140 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from f4:4d:30:63:75:82 (oui Unknown), length 347
|10:52:37.200771 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from f4:4d:30:63:75:82 (oui Unknown), length 359
|10:52:40.846979 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from f4:4d:30:63:75:82 (oui Unknown), length 385
|10:52:43.077918 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from f4:4d:30:63:75:82 (oui Unknown), length 385
|10:52:47.087553 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from f4:4d:30:63:75:82 (oui Unknown), length 397
|10:52:59.920696 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from f4:4d:30:63:75:82 (oui Unknown), length 300
|10:52:59.922192 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from f4:4d:30:63:75:82 (oui Unknown), length 300
|$ tcpdump -r rpi.pcap port bootpc
|reading from file rpi.pcap, link-type EN10MB (Ethernet), snapshot length 262144
|10:48:00.072173 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from dc:a6:32:78:98:ae (oui Unknown), length 322
|10:48:00.073839 IP 192.168.67.1.bootps > 192.168.67.53.bootpc: BOOTP/DHCP, Reply, length 383
|10:48:00.132078 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from dc:a6:32:78:98:ae (oui Unknown), length 309
|10:48:00.178385 IP 192.168.67.1.bootps > 192.168.67.53.bootpc: BOOTP/DHCP, Reply, length 302
|10:48:40.737311 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from dc:a6:32:78:98:ae (oui Unknown), length 548
|10:48:40.740809 IP 192.168.67.1.bootps > 192.168.67.53.bootpc: BOOTP/DHCP, Reply, length 300
|10:48:40.745292 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from dc:a6:32:78:98:ae (oui Unknown), length 548
|10:48:40.799629 IP 192.168.67.1.bootps > 192.168.67.53.bootpc: BOOTP/DHCP, Reply, length 300
|10:48:44.933942 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from dc:a6:32:78:98:ae (oui Unknown), length 300
|10:48:44.938204 IP 192.168.67.1.bootps > 192.168.67.53.bootpc: BOOTP/DHCP, Reply, length 300
|10:48:44.938785 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from dc:a6:32:78:98:ae (oui Unknown), length 300
|10:48:44.983179 IP 192.168.67.1.bootps > 192.168.67.53.bootpc: BOOTP/DHCP, Reply, length 301
|$
What `tshark` says about it.
Note the packet count and the time offset (columns 1 and 2)
and that there are three transactions.
|$ tshark -nr rpi.pcap | grep DHCP
| 1 0.000000 0.0.0.0 → 255.255.255.255 DHCP 364 DHCP Discover - Transaction ID 0x6e9ddeb7
| 2 0.001666 192.168.67.1 → 192.168.67.53 DHCP 425 DHCP Offer - Transaction ID 0x6e9ddeb7
| 3 0.059905 0.0.0.0 → 255.255.255.255 DHCP 351 DHCP Request - Transaction ID 0x6e9ddeb7
| 7 0.106212 192.168.67.1 → 192.168.67.53 DHCP 344 DHCP ACK - Transaction ID 0x6e9ddeb7
|119315 40.665138 0.0.0.0 → 255.255.255.255 DHCP 590 DHCP Discover - Transaction ID 0x378f8d8b
|119316 40.668636 192.168.67.1 → 192.168.67.53 DHCP 342 DHCP Offer - Transaction ID 0x378f8d8b
|119317 40.673119 0.0.0.0 → 255.255.255.255 DHCP 590 DHCP Request - Transaction ID 0x378f8d8b
|119318 40.727456 192.168.67.1 → 192.168.67.53 DHCP 342 DHCP ACK - Transaction ID 0x378f8d8b
|119324 44.861769 0.0.0.0 → 255.255.255.255 DHCP 342 DHCP Discover - Transaction ID 0x6f84b210
|119325 44.866031 192.168.67.1 → 192.168.67.53 DHCP 342 DHCP Offer - Transaction ID 0x6f84b210
|119326 44.866612 0.0.0.0 → 255.255.255.255 DHCP 342 DHCP Request - Transaction ID 0x6f84b210
|119327 44.911006 192.168.67.1 → 192.168.67.53 DHCP 343 DHCP ACK - Transaction ID 0x6f84b210
|$
Tcpdump Verbose, `-v`, of that:
$ tcpdump -nr rpi.pcap -v port bootpc
reading from file rpi.pcap, link-type EN10MB (Ethernet), snapshot length 262144
10:48:00.072173 IP (tos 0x0, ttl 64, id 20588, offset 0, flags [none], proto UDP (17), length 350)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from dc:a6:32:78:98:ae, length 322, xid 0x6e9ddeb7, Flags [none]
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Discover
Parameter-Request (55), length 14:
Subnet-Mask (1), Default-Gateway (3), Vendor-Option (43), Vendor-Class (60)
TFTP (66), BF (67), Unknown (128), Unknown (129)
Unknown (130), Unknown (131), Unknown (132), Unknown (133)
Unknown (134), Unknown (135)
Vendor-Class (60), length 32: "PXEClient:Arch:00000:UNDI:002001"
ARCH (93), length 2: 0
NDI (94), length 3: 1.2.1
GUID (97), length 17: 0.82.80.105.52.18.49.192.0.50.120.152.174.94.119.158.94
10:48:00.073839 IP (tos 0xc0, ttl 64, id 5852, offset 0, flags [none], proto UDP (17), length 411)
192.168.67.1.67 > 192.168.67.53.68: BOOTP/DHCP, Reply, length 383, xid 0x6e9ddeb7, Flags [none]
Your-IP 192.168.67.53
Server-IP 192.168.67.1
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Offer
Server-ID (54), length 4: 192.168.67.1
Lease-Time (51), length 4: 43200
BF (67), length 19: "ltsp/undionly.kpxe^@"
RN (58), length 4: 21600
RB (59), length 4: 37800
Subnet-Mask (1), length 4: 255.255.255.0
BR (28), length 4: 192.168.67.255
Default-Gateway (3), length 4: 192.168.67.1
Vendor-Class (60), length 9: "PXEClient"
GUID (97), length 17: 0.82.80.105.52.18.49.192.0.50.120.152.174.94.119.158.94
Vendor-Option (43), length 44: 6.1.3.10.4.0.80.88.69.8.7.128.4.1.192.168.67.1.9.23.128.4.20.82.97.115.112.98.101.114.114.121.32.80.105.32.66.111.111.116.32.32.32.255
10:48:00.132078 IP (tos 0x0, ttl 64, id 20590, offset 0, flags [none], proto UDP (17), length 337)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from dc:a6:32:78:98:ae, length 309, xid 0x6e9ddeb7, Flags [none]
Server-IP 192.168.67.1
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Request
Requested-IP (50), length 4: 192.168.67.53
Server-ID (54), length 4: 192.168.67.1
Vendor-Class (60), length 32: "PXEClient:Arch:00000:UNDI:002001"
GUID (97), length 17: 0.82.80.105.52.18.49.192.0.50.120.152.174.94.119.158.94
10:48:00.178385 IP (tos 0xc0, ttl 64, id 5869, offset 0, flags [none], proto UDP (17), length 330)
192.168.67.1.67 > 192.168.67.53.68: BOOTP/DHCP, Reply, length 302, xid 0x6e9ddeb7, Flags [none]
Your-IP 192.168.67.53
Server-IP 192.168.67.1
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: ACK
Server-ID (54), length 4: 192.168.67.1
Lease-Time (51), length 4: 43200
RN (58), length 4: 21600
RB (59), length 4: 37800
Subnet-Mask (1), length 4: 255.255.255.0
BR (28), length 4: 192.168.67.255
Default-Gateway (3), length 4: 192.168.67.1
LOG (7), length 4: 192.168.67.1
Domain-Name-Server (6), length 8: 8.8.8.8,8.8.8.8
10:48:40.737311 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 576)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from dc:a6:32:78:98:ae, length 548, xid 0x378f8d8b, Flags [none]
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Discover
Parameter-Request (55), length 9:
Subnet-Mask (1), Default-Gateway (3), Domain-Name-Server (6), Hostname (12)
Domain-Name (15), RP (17), MTU (26), YD (40)
NTP (42)
10:48:40.740809 IP (tos 0xc0, ttl 64, id 3785, offset 0, flags [none], proto UDP (17), length 328)
192.168.67.1.67 > 192.168.67.53.68: BOOTP/DHCP, Reply, length 300, xid 0x378f8d8b, Flags [none]
Your-IP 192.168.67.53
Server-IP 192.168.67.1
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Offer
Server-ID (54), length 4: 192.168.67.1
Lease-Time (51), length 4: 43200
RN (58), length 4: 21600
RB (59), length 4: 37800
Subnet-Mask (1), length 4: 255.255.255.0
BR (28), length 4: 192.168.67.255
Default-Gateway (3), length 4: 192.168.67.1
Domain-Name-Server (6), length 8: 8.8.8.8,8.8.8.8
10:48:40.745292 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 576)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from dc:a6:32:78:98:ae, length 548, xid 0x378f8d8b, Flags [none]
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Request
Server-ID (54), length 4: 192.168.67.1
Requested-IP (50), length 4: 192.168.67.53
Parameter-Request (55), length 9:
Subnet-Mask (1), Default-Gateway (3), Domain-Name-Server (6), Hostname (12)
Domain-Name (15), RP (17), MTU (26), YD (40)
NTP (42)
10:48:40.799629 IP (tos 0xc0, ttl 64, id 3788, offset 0, flags [none], proto UDP (17), length 328)
192.168.67.1.67 > 192.168.67.53.68: BOOTP/DHCP, Reply, length 300, xid 0x378f8d8b, Flags [none]
Your-IP 192.168.67.53
Server-IP 192.168.67.1
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: ACK
Server-ID (54), length 4: 192.168.67.1
Lease-Time (51), length 4: 43200
RN (58), length 4: 21600
RB (59), length 4: 37800
Subnet-Mask (1), length 4: 255.255.255.0
BR (28), length 4: 192.168.67.255
Default-Gateway (3), length 4: 192.168.67.1
Domain-Name-Server (6), length 8: 8.8.8.8,8.8.8.8
10:48:44.933942 IP (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from dc:a6:32:78:98:ae, length 300, xid 0x6f84b210, Flags [none]
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Discover
Hostname (12), length 13: "192.168.67.53"
Parameter-Request (55), length 13:
Subnet-Mask (1), BR (28), Time-Zone (2), Default-Gateway (3)
Domain-Name (15), Domain-Name-Server (6), Unknown (119), Hostname (12)
Netbios-Name-Server (44), Netbios-Scope (47), MTU (26), Classless-Static-Route (121)
NTP (42)
10:48:44.938204 IP (tos 0xc0, ttl 64, id 3933, offset 0, flags [none], proto UDP (17), length 328)
192.168.67.1.67 > 192.168.67.53.68: BOOTP/DHCP, Reply, length 300, xid 0x6f84b210, Flags [none]
Your-IP 192.168.67.53
Server-IP 192.168.67.1
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Offer
Server-ID (54), length 4: 192.168.67.1
Lease-Time (51), length 4: 43200
RN (58), length 4: 21600
RB (59), length 4: 37800
Subnet-Mask (1), length 4: 255.255.255.0
BR (28), length 4: 192.168.67.255
Default-Gateway (3), length 4: 192.168.67.1
Domain-Name-Server (6), length 8: 8.8.8.8,8.8.8.8
10:48:44.938785 IP (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from dc:a6:32:78:98:ae, length 300, xid 0x6f84b210, Flags [none]
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Request
Server-ID (54), length 4: 192.168.67.1
Requested-IP (50), length 4: 192.168.67.53
Hostname (12), length 13: "192.168.67.53"
Parameter-Request (55), length 13:
Subnet-Mask (1), BR (28), Time-Zone (2), Default-Gateway (3)
Domain-Name (15), Domain-Name-Server (6), Unknown (119), Hostname (12)
Netbios-Name-Server (44), Netbios-Scope (47), MTU (26), Classless-Static-Route (121)
NTP (42)
10:48:44.983179 IP (tos 0xc0, ttl 64, id 3934, offset 0, flags [none], proto UDP (17), length 329)
192.168.67.1.67 > 192.168.67.53.68: BOOTP/DHCP, Reply, length 301, xid 0x6f84b210, Flags [none]
Your-IP 192.168.67.53
Server-IP 192.168.67.1
Client-Ethernet-Address dc:a6:32:78:98:ae
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: ACK
Server-ID (54), length 4: 192.168.67.1
Lease-Time (51), length 4: 43200
RN (58), length 4: 21600
RB (59), length 4: 37800
Subnet-Mask (1), length 4: 255.255.255.0
BR (28), length 4: 192.168.67.255
Default-Gateway (3), length 4: 192.168.67.1
Hostname (12), length 3: "192"
Domain-Name-Server (6), length 8: 8.8.8.8,8.8.8.8
More in the next message.
Groeten
Geert Stappers
--
Silence is hard to parse
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