David Miller <da...@davemloft.net> writes: >> When creating veth pair, at first rtnl_new_link() creates veth_dev, i.e. >> one end of the veth pipe, but not registers it; then veth_newlink() gets >> invoked, where peer dev is created _and_ registered, followed by veth_dev >> registration, which may fail if peer information, that is VETH_INFO_PEER >> attribute, has not been provided and the kernel will allocate unique veth >> name. >> >> So, we should ask the kernel to allocate unique name for veth_dev only >> when peer info is not available. >> >> Example: >> >> % ip link dev veth0 type veth >> RTNETLINK answers: File exists >> >> After fix: >> % ip link dev veth0 type veth >> % ip link show dev veth0 >> 5: veth0@veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode >> DEFAULT group default qlen 1000 >> link/ether f6:ef:8b:96:f4:ec brd ff:ff:ff:ff:ff:ff >> % >> >> Signed-off-by: Roman Mashak <m...@mojatatu.com> > > I'm not so sure about this. > > If we specify an explicit tb[IFLA_NAME], we shouldn't completely ignore that > request from the user just because they didn't give any peer information. > > I see what happens in this case, the peer gets 'veth0' and then since > the user asked for 'veth0' for the non-peer it conflicts.
So, the only way is to require user space to _always_ pass in VETH_INFO_PEER, which may break existing code (fixing iproute2 is easiest). Otherwise ignore netlink messages lacking of VETH_INFO_PEER and return error. IMO, neither of these solutions seem reasonable. Also, there are valid use cases where a user does not care about veth name sitting in container, but assigns a name following certain pattern to a host-side veth. > Well, too bad. The user must work to orchestrate things such that > this doesn't happen. That means either providing the IFLA_NAME for > both the peer and the non-peer, or specifying neither. > > I'm not applying this, sorry.
