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authorStefano Brivio <sbrivio@redhat.com>2022-11-02 23:44:25 +0100
committerStefano Brivio <sbrivio@redhat.com>2022-11-04 12:04:32 +0100
commit7656a6f8888237b9e23d63666e921528b6aaf950 (patch)
tree655d7f88ab30fac72f6502597431f72c018ba5ff /tap.c
parentde93acbe7056e392ed759675e38ccc84eb1a56bf (diff)
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conf: Adjust netmask on mismatch between IPv4 address/netmask and gateway
Seen in a Google Compute Engine environment with a machine configured via cloud-init-dhcp, while testing Podman integration for pasta: the assigned address has a /32 netmask, and there's a default route, which can be added on the host because there's another route, also /32, pointing to the default gateway. For example, on the host: ip -4 address add 10.156.0.2/32 dev eth0 ip -4 route add 10.156.0.1/32 dev eth0 ip -4 route add default via 10.156.0.1 This is not a valid configuration as far as I can tell: if the address is configured as /32, it shouldn't be used to reach a gateway outside its derived netmask. However, Linux allows that, and everything works. The problem comes when pasta --config-net sources address and default route from the host, and it can't configure the route in the target namespace because the gateway is invalid. That is, we would skip configuring the first route in the example, which results in the equivalent of doing: ip -4 address add 10.156.0.2/32 dev eth0 ip -4 route add default via 10.156.0.1 where, at this point, 10.156.0.1 is unreachable, and hence invalid as a gateway. Sourcing more routes than just the default is doable, but probably undesirable: pasta users want to provide connectivity to a container, not reflect exactly whatever trickery is configured on the host. Add a consistency check and an adjustment: if the configured default gateway is not reachable, shrink the given netmask until we can reach it. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Diffstat (limited to 'tap.c')
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