Bug 218700
| Summary: | the arp table may contain a fake IP address | ||
|---|---|---|---|
| Product: | Networking | Reporter: | Sergey (a_s_y) |
| Component: | IPV4 | Assignee: | Stephen Hemminger (stephen) |
| Status: | NEW --- | ||
| Severity: | normal | ||
| Priority: | P3 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Kernel Version: | 5.10 | Subsystem: | |
| Regression: | No | Bisected commit-id: | |
Kernel version 5.10.145 # sysctl -a | grep proxy_arp | grep "ether9.3109\|ether1.2115\|all" net.ipv4.conf.all.proxy_arp = 0 net.ipv4.conf.all.proxy_arp_pvlan = 0 net.ipv4.conf.ether1/2115.proxy_arp = 0 net.ipv4.conf.ether1/2115.proxy_arp_pvlan = 0 net.ipv4.conf.ether9/3109.proxy_arp = 0 net.ipv4.conf.ether9/3109.proxy_arp_pvlan = 0 |
An entry from an incorrect interface may get into the arp table: # arp -n|grep 100.64.1.113 100.64.1.113 ether 50:ff:20:26:fa:14 C ether9.3109 100.64.1.113 (incomplete) ether1.2115 # ip -4 a s dev ether9.3109 1829: ether9.3109@ether9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 inet 100.64.3.62/30 brd 100.64.3.63 scope global ether9.3109 valid_lft forever preferred_lft forever # ip -4 a s dev ether1.2115 1822: ether1.2115@ether1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 inet 100.64.1.114/30 brd 100.64.1.115 scope global ether1.2115 valid_lft forever preferred_lft forever ether9.3109 and ether1.2115 are 802.1q VLAN, I don't know if it's important. The ether9.3109 interface receives traffic from forgotten hardware (tcpdump -e -ni ether9 host 100.64.1.113): 10:57:08.861954 50:ff:20:26:fa:14 > Broadcast, ethertype 802.1Q (0x8100), length 64: vlan 3109, p 0, ethertype ARP, Request who-has 100.64.1.114 tell 100.64.1.113, length 46 kernel reply is 1) exists, although the ether9.3109 interface does not contain 100.64.1.114 2) contain the MAC of ether9.3109: 10:57:08.861972 3c:ec:ef:4d:94:ee > 50:ff:20:26:fa:14, ethertype 802.1Q (0x8100), length 46: vlan 3109, p 0, ethertype ARP, Reply 100.64.1.114 is-at 3c:ec:ef:4d:94:ee, length 28 # ip a| grep 100.64.1.114 inet 100.64.1.114/30 brd 100.64.1.115 scope global ether1.2115