Por que você chama a resposta ARP de "errado"? O endereço IP do sistema pode certamente ser alcançado através dessa interface. É por isso que a resposta ARP é enviada para começar. Não fazer isso pode fazer com que algum tráfego flua por meio de caminhos menos ideais ou de forma alguma. Por exemplo, tap0 pode ser uma conexão VPN e essa resposta ARP ajuda a garantir que o tráfego para o outro endereço IP flua corretamente por meio da VPN.
Se você realmente quiser fazer isso, defina os sysctls arp_ignore
e arp_announce
para valores desejados.
arp_announce - INTEGER Define different restriction levels for announcing the local source IP address from IP packets in ARP requests sent on interface: 0 - (default) Use any local address, configured on any interface 1 - Try to avoid local addresses that are not in the target's subnet for this interface. This mode is useful when target hosts reachable via this interface require the source IP address in ARP requests to be part of their logical network configured on the receiving interface. When we generate the request we will check all our subnets that include the target IP and will preserve the source address if it is from such subnet. If there is no such subnet we select source address according to the rules for level 2. 2 - Always use the best local address for this target. In this mode we ignore the source address in the IP packet and try to select local address that we prefer for talks with the target host. Such local address is selected by looking for primary IP addresses on all our subnets on the outgoing interface that include the target IP address. If no suitable local address is found we select the first local address we have on the outgoing interface or on all other interfaces, with the hope we will receive reply for our request and even sometimes no matter the source IP address we announce. The max value from conf/{all,interface}/arp_announce is used. Increasing the restriction level gives more chance for receiving answer from the resolved target while decreasing the level announces more valid sender's information.
E arp_ignore
é descrito como:
arp_ignore - INTEGER Define different modes for sending replies in response to received ARP requests that resolve local target IP addresses: 0 - (default): reply for any local target IP address, configured on any interface 1 - reply only if the target IP address is local address configured on the incoming interface 2 - reply only if the target IP address is local address configured on the incoming interface and both with the sender's IP address are part from same subnet on this interface 3 - do not reply for local addresses configured with scope host, only resolutions for global and link addresses are replied 4-7 - reserved 8 - do not reply for all local addresses The max value from conf/{all,interface}/arp_ignore is used when ARP request is received on the {interface}
Então, você desejaria definir arp_ignore
para 1 (ou possivelmente 2) e arp_announce
para 2.
net.ipv4.conf.all.arp_ignore=1
net.ipv4.conf.all.arp_announce=2
Para testes, provavelmente é bom fazer isso. Mas um sistema de produção real provavelmente se comportará da maneira que você experimentou, e seu programa precisa ser capaz de lidar com isso.