My older patches are obsolete, now that glibc 2.11 supports RES_USE_DNSSEC and fixed an EDNS-related bug.
I backported the changes to the glibc versions used in Ubuntu 9.04 (Jaunty Jackalope) and 9.10 (Karmic Koala) as well as Debian Lenny:
- Ubuntu 9.04: backported RES_USE_DNSSEC patch for glibc 2.9
- Ubuntu 9.10: backported RES_USE_DNSSEC patch for eglibc 2.10.1
- Debian Lenny: backported RES_USE_DNSSEC patch for glibc 2.7
Binary packages for Ubuntu are available from my Personal Package Archive.