proxy_arp's DHCP snooper does not recognize the following DHCP response

rany rany2 at riseup.net
Tue Apr 18 04:34:22 PDT 2023


I'm not sure if this is helpful but I believe this is the only device 
which does not have a DHCP hostname set. Whether that is related or just 
a coincidence, I do not know.


On 4/18/23 14:29, rany wrote:
> Hello,
>
> My Pixel 6 phone running GrapheneOS does not get recognized by the 
> DHCP snooper that is used by proxy_arp is enabled.
>
> If any additional information is needed, I'm more than willing to 
> provide it. (Also: apologies if this isn't the right place to report 
> this, in the case that I'm in the wrong place please let me know where 
> to take this report)
>
> Below is the tcpdump of the DHCP messages in question:
>
> 14:27:08.429655 6a:85:25:53:52:87 > ff:ff:ff:ff:ff:ff, ethertype IPv4 
> (0x0800), length 330: (tos 0x10, ttl 64, id 0, offset 0, flags [DF], 
> proto UDP (17), length 316)
>     0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 
> 6a:85:25:53:52:87, length 288, xid 0x7cc4d1b2, Flags [none]
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: Discover
>         Client-ID (61), length 7: ether 6a:85:25:53:52:87
>         MSZ (57), length 2: 1500
>         Vendor-Class (60), length 15: "android-dhcp-13"
>         Parameter-Request (55), length 12:
>           Subnet-Mask (1), Default-Gateway (3), Domain-Name-Server 
> (6), Domain-Name (15)
>           MTU (26), BR (28), Lease-Time (51), RN (58)
>           RB (59), Vendor-Option (43), URL (114), Unknown (108)
> 14:27:09.439824 6a:85:25:53:52:87 > ff:ff:ff:ff:ff:ff, ethertype IPv4 
> (0x0800), length 330: (tos 0x10, ttl 64, id 0, offset 0, flags [DF], 
> proto UDP (17), length 316)
>     0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 
> 6a:85:25:53:52:87, length 288, xid 0x7cc4d1b2, secs 1, Flags [none]
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: Discover
>         Client-ID (61), length 7: ether 6a:85:25:53:52:87
>         MSZ (57), length 2: 1500
>         Vendor-Class (60), length 15: "android-dhcp-13"
>         Parameter-Request (55), length 12:
>           Subnet-Mask (1), Default-Gateway (3), Domain-Name-Server 
> (6), Domain-Name (15)
>           MTU (26), BR (28), Lease-Time (51), RN (58)
>           RB (59), Vendor-Option (43), URL (114), Unknown (108)
> 14:27:11.461546 6a:85:25:53:52:87 > ff:ff:ff:ff:ff:ff, ethertype IPv4 
> (0x0800), length 330: (tos 0x10, ttl 64, id 0, offset 0, flags [DF], 
> proto UDP (17), length 316)
>     0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 
> 6a:85:25:53:52:87, length 288, xid 0x7cc4d1b2, secs 3, Flags [none]
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: Discover
>         Client-ID (61), length 7: ether 6a:85:25:53:52:87
>         MSZ (57), length 2: 1500
>         Vendor-Class (60), length 15: "android-dhcp-13"
>         Parameter-Request (55), length 12:
>           Subnet-Mask (1), Default-Gateway (3), Domain-Name-Server 
> (6), Domain-Name (15)
>           MTU (26), BR (28), Lease-Time (51), RN (58)
>           RB (59), Vendor-Option (43), URL (114), Unknown (108)
> 14:27:12.004533 00:20:91:aa:78:3b > 6a:85:25:53:52:87, ethertype IPv4 
> (0x0800), length 351: (tos 0xc0, ttl 64, id 27411, offset 0, flags 
> [none], proto UDP (17), length 337)
>     10.146.80.1.67 > 10.146.83.135.68: BOOTP/DHCP, Reply, length 309, 
> xid 0x7cc4d1b2, Flags [none]
>       Your-IP 10.146.83.135
>       Server-IP 10.146.80.1
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: Offer
>         Server-ID (54), length 4: 10.146.80.1
>         Lease-Time (51), length 4: 3600
>         RN (58), length 4: 1800
>         RB (59), length 4: 3150
>         Subnet-Mask (1), length 4: 255.255.240.0
>         BR (28), length 4: 10.146.95.255
>         Default-Gateway (3), length 4: 10.146.80.1
>         Domain-Name-Server (6), length 4: 10.146.80.1
>         Domain-Name (15), length 11: "rlan.eu.org"
>         MTU (26), length 2: 1500
> 14:27:12.005570 00:20:91:aa:78:3b > 6a:85:25:53:52:87, ethertype IPv4 
> (0x0800), length 351: (tos 0xc0, ttl 64, id 27412, offset 0, flags 
> [none], proto UDP (17), length 337)
>     10.146.80.1.67 > 10.146.83.135.68: BOOTP/DHCP, Reply, length 309, 
> xid 0x7cc4d1b2, secs 1, Flags [none]
>       Your-IP 10.146.83.135
>       Server-IP 10.146.80.1
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: Offer
>         Server-ID (54), length 4: 10.146.80.1
>         Lease-Time (51), length 4: 3600
>         RN (58), length 4: 1800
>         RB (59), length 4: 3150
>         Subnet-Mask (1), length 4: 255.255.240.0
>         BR (28), length 4: 10.146.95.255
>         Default-Gateway (3), length 4: 10.146.80.1
>         Domain-Name-Server (6), length 4: 10.146.80.1
>         Domain-Name (15), length 11: "rlan.eu.org"
>         MTU (26), length 2: 1500
> 14:27:12.006471 00:20:91:aa:78:3b > 6a:85:25:53:52:87, ethertype IPv4 
> (0x0800), length 351: (tos 0xc0, ttl 64, id 27413, offset 0, flags 
> [none], proto UDP (17), length 337)
>     10.146.80.1.67 > 10.146.83.135.68: BOOTP/DHCP, Reply, length 309, 
> xid 0x7cc4d1b2, secs 3, Flags [none]
>       Your-IP 10.146.83.135
>       Server-IP 10.146.80.1
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: Offer
>         Server-ID (54), length 4: 10.146.80.1
>         Lease-Time (51), length 4: 3600
>         RN (58), length 4: 1800
>         RB (59), length 4: 3150
>         Subnet-Mask (1), length 4: 255.255.240.0
>         BR (28), length 4: 10.146.95.255
>         Default-Gateway (3), length 4: 10.146.80.1
>         Domain-Name-Server (6), length 4: 10.146.80.1
>         Domain-Name (15), length 11: "rlan.eu.org"
>         MTU (26), length 2: 1500
> 14:27:12.121619 6a:85:25:53:52:87 > ff:ff:ff:ff:ff:ff, ethertype IPv4 
> (0x0800), length 342: (tos 0x10, ttl 64, id 0, offset 0, flags [DF], 
> proto UDP (17), length 328)
>     0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 
> 6a:85:25:53:52:87, length 300, xid 0x7cc4d1b2, secs 3, Flags [none]
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: Request
>         Client-ID (61), length 7: ether 6a:85:25:53:52:87
>         Requested-IP (50), length 4: 10.146.83.135
>         Server-ID (54), length 4: 10.146.80.1
>         MSZ (57), length 2: 1500
>         Vendor-Class (60), length 15: "android-dhcp-13"
>         Parameter-Request (55), length 12:
>           Subnet-Mask (1), Default-Gateway (3), Domain-Name-Server 
> (6), Domain-Name (15)
>           MTU (26), BR (28), Lease-Time (51), RN (58)
>           RB (59), Vendor-Option (43), URL (114), Unknown (108)
> 14:27:12.158395 00:20:91:aa:78:3b > 6a:85:25:53:52:87, ethertype IPv4 
> (0x0800), length 351: (tos 0xc0, ttl 64, id 27414, offset 0, flags 
> [none], proto UDP (17), length 337)
>     10.146.80.1.67 > 10.146.83.135.68: BOOTP/DHCP, Reply, length 309, 
> xid 0x7cc4d1b2, secs 3, Flags [none]
>       Your-IP 10.146.83.135
>       Server-IP 10.146.80.1
>       Client-Ethernet-Address 6a:85:25:53:52:87
>       Vendor-rfc1048 Extensions
>         Magic Cookie 0x63825363
>         DHCP-Message (53), length 1: ACK
>         Server-ID (54), length 4: 10.146.80.1
>         Lease-Time (51), length 4: 3600
>         RN (58), length 4: 1800
>         RB (59), length 4: 3150
>         Subnet-Mask (1), length 4: 255.255.240.0
>         BR (28), length 4: 10.146.95.255
>         Default-Gateway (3), length 4: 10.146.80.1
>         Domain-Name-Server (6), length 4: 10.146.80.1
>         Domain-Name (15), length 11: "rlan.eu.org"
>         MTU (26), length 2: 1500
>
> Thank you,
> rany
>
>
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