When running iperf the -i flag doesn't give valid output and causes the program to enter an infinite loop. It doesn't seem to matter whether it's in server or client mode. I downloaded the source and compiled it, and on that version the -i flag worked perfectly. Possible ebuild problem.
*** Bug 145210 has been marked as a duplicate of this bug. ***
Which version? Also, post emerge --info please.
I tried copying the source for iperf from /usr/portage/distfiles. untaring, and compiling it. When I did that the -i flag worked perfectly. I'm using iperf-2.0.1, the latest in stable. Portage 2.1-r2 (default-linux/x86/2005.1, gcc-3.4.6, glibc-2.3.6-r4, 2.6.16-gentoo-r7 i686) ================================================================= System uname: 2.6.16-gentoo-r7 i686 AMD Athlon(tm) Processor Gentoo Base System version 1.12.4 distcc 2.18.3 i686-pc-linux-gnu (protocols 1 and 2) (default port 3632) [disabled] ccache version 2.3 [enabled] app-admin/eselect-compiler: [Not Present] dev-lang/python: 2.3.5-r2, 2.4.3-r1 dev-python/pycrypto: 2.0.1-r5 dev-util/ccache: 2.3 dev-util/confcache: [Not Present] sys-apps/sandbox: 1.2.17 sys-devel/autoconf: 2.13, 2.59-r7 sys-devel/automake: 1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2 sys-devel/binutils: 2.16.1-r3 sys-devel/gcc-config: 1.3.13-r3 sys-devel/libtool: 1.5.22 virtual/os-headers: 2.6.11-r2 ACCEPT_KEYWORDS="x86" AUTOCLEAN="yes" CBUILD="i686-pc-linux-gnu" CFLAGS="-march=athlon-tbird -O3 -pipe" CHOST="i686-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/kde/3.5/env /usr/kde/3.5/share/config /usr/kde/3.5/shutdown /usr/share/X11/xkb /usr/share/config" CONFIG_PROTECT_MASK="/etc/env.d /etc/gconf /etc/revdep-rebuild /etc/terminfo" CXXFLAGS="-march=athlon-tbird -O3 -pipe" DISTDIR="/usr/portage/distfiles" FEATURES="autoconfig ccache distlocks metadata-transfer sandbox sfperms strict" GENTOO_MIRRORS="ftp://194.117.143.72/mirrors/gentoo http://ftp.ntua.gr/pub/linux/gentoo/ http://gentoo.chem.wisc.edu/gentoo/ ftp://ftp.ussg.iu.edu/pub/linux/gentoo ftp://gentoo.mirrors.tds.net/gentoo" MAKEOPTS="-j2" PKGDIR="/usr/portage/packages" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --delete-after --stats --timeout=180 --exclude='/distfiles' --exclude='/local' --exclude='/packages'" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" SYNC="rsync://192.168.1.154/portage" USE="X alsa apm arts avi berkdb bitmap-fonts bzip2 cdr cli crypt cups dlloader dri dvdr dvdread eds emboss encode flac foomaticdb fortran gdbm gif gpm gstreamer gtk gtk2 imlib ipv6 isdnlog java jpeg kde libg++ libwww mad mikmod motif mp3 mpeg ncurses nls ogg oggvorbis opengl oss pam pcre pdflib perl png pppd python qt qt3 qt4 quicktime readline reflection sdl session spell spl ssl tcpd tiff truetype truetype-fonts type1-fonts vorbis x86 xml2 xmms xorg xv zlib elibc_glibc input_devices_keyboard input_devices_mouse input_devices_evdev kernel_linux userland_GNU video_cards_fglrx" Unset: CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LANG, LC_ALL, LDFLAGS, LINGUAS, PORTAGE_RSYNC_EXTRA_OPTS, PORTDIR_OVERLAY
I tried 2.0.2 and it works for me. Feel free to reopen if it doesn't work for you with 2.0.2