Currently, ppp does not install its header files (pppd.h and others). These are needed by the pptp plugin of NetworkManager (not yet in portage). From ppp-2.4.4/pppd/Makefile HEADERS = ccp.h chap-new.h ecp.h fsm.h ipcp.h \ ipxcp.h lcp.h magic.h md5.h patchlevel.h pathnames.h pppd.h \ upap.h eap.h mplscp.h ... install-devel: mkdir -p $(INCDIR)/pppd $(INSTALL) -c -m 644 $(HEADERS) $(INCDIR)/pppd
Usually pppd dependent packages have all the necessary pppd header files included in their source tree and ebuild do nothing more than correcting the PPPD_VER (see net-dialup/pptpd). What header files do you need?
The nm-pppt plugin ships with several versions of the ppp header files and allows to specify the version to use in ./configure. So it would work with the code from the ptpd ebuild. But it also allows to link to a given ppp include dir and figures out the version itself. From a maintenance point of view, I don't understand why packages would want to do the first thing. This creates a lot of work when a new ppp version should come out, because I'd need to patch nm-pptp to contain the new headers. As for your question, it needs fsm.h, ipcp.h, patchlevel.h and pppd.h. But if you decide to install the headers, why not all of them? Debian's ppp-devel ships with the whole list: http://packages.debian.org/cgi-bin/search_contents.pl?searchmode=filelist&word=ppp-dev
Fixed in 2.4.4-r9 by running make install-devel in src_install(). I will ask arch teams to stabilize it.
