error in autoconf

[Aben Siatris]

checking netinet/tcp.h usability... yes
checking netinet/tcp.h presence... yes
checking for netinet/tcp.h... yes
checking netinet/udp.h usability... yes
checking netinet/udp.h presence... yes
checking for netinet/udp.h... yes
checking ethertype.h usability... no
checking ethertype.h presence... no
checking for ethertype.h... no
checking pcap.h usability... yes
checking pcap.h presence... yes
checking for pcap.h... yes
checking linux/if_pppox.h usability... no
checking linux/if_pppox.h presence... yes
configure: WARNING: linux/if_pppox.h: present but cannot be compiled
configure: WARNING: linux/if_pppox.h: check for missing prerequisite headers?
configure: WARNING: linux/if_pppox.h: proceeding with the preprocessor's result
configure: WARNING:     ## ------------------------------------ ##
configure: WARNING:     ## Report this to address@hidden ##
configure: WARNING:     ## ------------------------------------ ##
checking for linux/if_pppox.h... yes
checking crypt.h usability... yes
checking crypt.h presence... yes
checking for crypt.h... yes
checking pwd.h usability... yes
checking pwd.h presence... yes
checking for pwd.h... yes
checking security/pam_appl.h usability... yes
checking security/pam_appl.h presence... yes
checking for security/pam_appl.h... yes
checking shadow.h usability... yes
checking shadow.h presence... yes
checking for shadow.h... yes


emerging ntop in Gentoo 1.4 ($emerge ntop)

$emerge info
Portage 2.0.49-r15 (default-x86-1.4, gcc-3.2.3, glibc-2.3.2-r3, 
2.4.20-gentoo-r8)
=================================================================
System uname: 2.4.20-gentoo-r8 i686 Intel(R) Celeron(TM) CPU                
1300MHz
Gentoo Base System version 1.4.3.10
ACCEPT_KEYWORDS="x86"
AUTOCLEAN="yes"
CFLAGS="-O3 -mcpu=pentium3 -funroll-loops -pipe -msse -mmmx"
CHOST="i686-pc-linux-gnu"
COMPILER="gcc3"
CONFIG_PROTECT="/etc /var/qmail/control /usr/kde/2/share/config 
/usr/kde/3/share/config 
/usr/X11R6/lib/X11/xkb /usr/kde/3.1/share/config /usr/share/config"
CONFIG_PROTECT_MASK="/etc/gconf /etc/env.d"
CXXFLAGS="-O3 -mcpu=pentium3 -funroll-loops -pipe -msse -mmmx"
DISTDIR="/usr/portage/distfiles"
FEATURES="sandbox ccache autoaddcvs"
GENTOO_MIRRORS="ftp://gentoo.inode.at/source/ http://gentoo.inode.at/ 
http://mirrors.sec.informatik.tu-darmstadt.de/gentoo 
http://212.219.247.18/sites/www.ibiblio.org/gentoo/";
MAKEOPTS="-j2"
PKGDIR="/usr/portage/packages"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
PORTDIR_OVERLAY=""
SYNC="rsync://rsync.gentoo.org/gentoo-portage"
USE="x86 oss apm avi crypt cups encode foomaticdb gif jpeg gnome libg++ libwww 
mad mikmod 
mpeg ncurses nls pdflib png quicktime spell truetype xml2 xmms xv zlib gdbm 
berkdb slang 
readline arts svga sdl gpm tcpd pam python esd imlib oggvorbis kde motif opengl 
icc dga dvb 
lirc ggi java bindist cdr directfb xkb nas nojoystick aalib -alsa nvidia nv X 
gtk2 cjk qt guile tcltk 
ruby ruby18 maildir curl flash javascript fbcon xml acl odbc ssl samba gtk perl 
threads sse mmx 
tiff"