Looks good to me. Thank you for taking care of it!

The 64-bit default prefixlen was removed at rev.277241. I did not notice it but I do not think it is a correct change because it has several bad side-effects. I will take a look at route.c by this weekend.

If I understand this correctly, when a 0xffff checksum comes in via wire and the receiving NIC has no RXCSUM offloading, dhclient with this patch does not check the checksum. Is this a correct behavior? I think the conditional (usum != 0xffff) should be added only when the NIC has IFCAP_RXCSUM and it is enabled. Whether this flag is activated or not can be obtained by SIOSGIFCAP ioctl (ifr->ifr_curcap).

Looks good to me.

Looks good to me, but you need to remove the names in contrib.committers.xml.

I think you need to add CFLAGS+=-DLIBWRAP in Makefile. The others look fine to me.

Looks good to me.

The cause is that the prefix route was removed by in_scrubprefix() in the PRC_IFDOWN handler and never reinstalled upon PRC_IFUP because the reinstallation is done only for ifa passed to SIOCAIFADDR. Just calling if_up(ifp) looks too heavy to me because it causes extra pr_ctlinput() calls of each protocol, not only inetdomain, in order to recover the routes. What do you think about adding reinstalltion of the prefix routes in the protocol specific PRC_IFUP handler instead?