Re: [libvirt] [PATCH] Determine the root physical interface of a given interface

In this patch I am adding functions that help to iteratively determine the root physical interface of a given interface. An example would be that a macvtap device is linked to eth0.100 which in turn is linked to eth0. Given the name or interface index of the macvtap device that is linked to eth0.100, eth0 is found by following the links to the end. I am using now the netlink library to parse the returned netlink messages and for that I am making additions to configure.ac and the rpm spec file to check for the netlink and netlink-devel packages respectively. In the configure.ac the requirement to have the netlink library is dependent on having macvtap. +static struct nla_policy ifla_policy[ IFLA_MAX + 1] = +{ + [IFLA_IFNAME ] = {.type = NLA_STRING }, + [IFLA_LINK] = {.type = NLA_U32 }, +};

+ + +static int +link_dump(int ifindex, const char *ifname, struct nlattr **tb, + char **recvbuf) +{ + int rc = 0; + char nlmsgbuf[256];

+ struct nlmsghdr *nlm = (struct nlmsghdr *)nlmsgbuf, *resp; + struct nlmsgerr *err; + char rtattbuf[64];

+ struct rtattr *rta; + struct ifinfomsg i = { + .ifi_family = AF_UNSPEC, + .ifi_index = ifindex + }; + int recvbuflen; + + *recvbuf = NULL; + + memset(&nlmsgbuf, 0, sizeof(nlmsgbuf));

+ + nlInit(nlm, NLM_F_REQUEST, RTM_GETLINK); + + if (!nlAppend(nlm, sizeof(nlmsgbuf), &i, sizeof(i))) + goto buffer_too_small; + + if (ifindex < 0 && ifname != NULL) { + rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_IFNAME, + ifname, strlen(ifname)+1);

+ if (!rta) + goto buffer_too_small; + + if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len)) + goto buffer_too_small; + } + + if (nlComm(nlm, recvbuf, &recvbuflen) < 0) + return -1; + + if (recvbuflen < NLMSG_LENGTH(0) || *recvbuf == NULL) + goto malformed_resp; + + resp = (struct nlmsghdr *)*recvbuf; + + switch (resp->nlmsg_type) { + case NLMSG_ERROR: + err = (struct nlmsgerr *)NLMSG_DATA(resp); + if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err))) + goto malformed_resp; + + switch (-err->error) { + case 0: + break; + + default:

+ virReportSystemError(-err->error, + _("error dumping %d interface"), + ifindex); + rc = -1; + } + break; + + case GENL_ID_CTRL: + case NLMSG_DONE: + if (nlmsg_parse(resp, sizeof(struct ifinfomsg), + tb, IFLA_MAX, ifla_policy)) { + goto malformed_resp; + } + break; + + default: + goto malformed_resp; + } + + if (rc != 0) + VIR_FREE(*recvbuf); + + return rc; + +malformed_resp: + macvtapError(VIR_ERR_INTERNAL_ERROR, "%s", + _("malformed netlink response message")); + VIR_FREE(*recvbuf); + return -1; + +buffer_too_small: + macvtapError(VIR_ERR_INTERNAL_ERROR, "%s", + _("internal buffer is too small")); + return -1; +} + + +/* TODO: move this into interface.c after moving netlink functions into + * utils dir + */ +/** + * ifaceGetNthParent + * + * @ifindex : the index of the interface or -1 if ifname is given + * @ifname : the name of the interface; ignored if ifindex is valid + * @nthParent : the nth parent interface to get + * @rootifname : pointer to buffer of size IFNAMSIZ + * @nth : the nth parent that is actually returned; if for example eth0.100 + * was given and the 100th parent is to be returned, then eth0 will + * most likely be returned with nth set to 1 since the chain does + * not have more interfaces + * + * Get the nth parent interface of the given interface. 0 is the interface + * itself. + * + * Return 0 on success, != 0 otherwise + */ +static int +ifaceGetNthParent(int ifindex, const char *ifname, unsigned int nthParent, + char *rootifname, unsigned int *nth) +{ + int rc; + struct nlattr *tb[IFLA_MAX + 1]; + char *recvbuf = NULL; + bool end = false; + unsigned int i = 0; + + while (!end && i <= nthParent) { + rc = link_dump(ifindex, ifname, tb, &recvbuf); + if (rc) + break; + + if (tb[IFLA_IFNAME]) { + if (!virStrcpy(rootifname, (char*)RTA_DATA(tb[IFLA_IFNAME]), + IFNAMSIZ)) { + macvtapError(VIR_ERR_INTERNAL_ERROR, "%s", + _("buffer for root interface name is too small")); + VIR_FREE(recvbuf); + return 1; + } + } + + if (tb[IFLA_LINK]) { + ifindex = *(int *)RTA_DATA(tb[IFLA_LINK]); + ifname = NULL; + } else + end = true; + + VIR_FREE(recvbuf); + + i++; + } + + if (nth) + *nth = i-1;

+ + return rc; +} + + +/** + * ifaceGetRootIface + * + * @ifindex : the index of the interface or -1 if ifname is given + * @ifname : the name of the interface; ignored if ifindex is valid + * @rootifname : pointer to buffer of size IFNAMSIZ + * + * Get the root interface of a given interface, i.e., if macvtap + * is linked to eth0.100, it will return eth0. + * + * Return 0 on success, != 0 otherwise + */ +static int +ifaceGetRootIface(int ifindex, const char *ifname, + char *rootifname) +{ + return ifaceGetNthParent(ifindex, ifname, ~0, rootifname, NULL); +} + + /* Open the macvtap's tap device. * @ifname: Name of the macvtap interface * @retries : Number of retries in case udev for example may need to be Index: libvirt-acl/src/Makefile.am =================================================================== --- libvirt-acl.orig/src/Makefile.am +++ libvirt-acl/src/Makefile.am @@ -932,7 +932,7 @@ libvirt_la_LDFLAGS = $(VERSION_SCRIPT_FL -version-info $(LIBVIRT_VERSION_INFO) \ $(COVERAGE_CFLAGS:-f%=-Wc,-f%) \ $(LIBXML_LIBS) \ - $(LIBPCAP_LIBS) \ + $(LIBPCAP_LIBS) $(LIBNL_LIBS) \ $(DRIVER_MODULE_LIBS) \ $(CYGWIN_EXTRA_LDFLAGS) $(MINGW_EXTRA_LDFLAGS) libvirt_la_CFLAGS = $(COVERAGE_CFLAGS) -DIN_LIBVIRT @@ -985,7 +985,7 @@ libvirt_lxc_SOURCES = \ $(NWFILTER_PARAM_CONF_SOURCES) libvirt_lxc_LDFLAGS = $(WARN_CFLAGS) $(COVERAGE_LDCFLAGS) $(CAPNG_LIBS) $(YAJL_LIBS) libvirt_lxc_LDADD = $(LIBXML_LIBS) $(NUMACTL_LIBS) $(LIB_PTHREAD) \ - ../gnulib/lib/libgnu.la + $(LIBNL_LIBS) ../gnulib/lib/libgnu.la

libvirt_lxc_CFLAGS = \ $(LIBPARTED_CFLAGS) \ $(NUMACTL_CFLAGS) \ Index: libvirt-acl/configure.ac =================================================================== --- libvirt-acl.orig/configure.ac +++ libvirt-acl/configure.ac @@ -42,6 +42,7 @@ HAL_REQUIRED=0.5.0 DEVMAPPER_REQUIRED=1.0.0 LIBCURL_REQUIRED="7.18.0" LIBPCAP_REQUIRED="1.0.0" +LIBNL_REQUIRED="1.1" dnl Checks for C compiler. AC_PROG_CC @@ -2005,6 +2006,24 @@ fi AM_CONDITIONAL([WITH_MACVTAP], [test "$with_macvtap" = "yes"]) +dnl netlink library + +LIBNL_CFLAGS="" +LIBNL_LIBS="" + +if test "$with_macvtap" = "yes"; then + PKG_CHECK_MODULES(LIBNL, libnl-1 >= $LIBNL_REQUIRED, [

+ ], [ + AC_MSG_ERROR([libnl >= $LIBNL_REQUIRED is required for macvtap support]) + ]) +fi + +AC_SUBST([LIBNL_CFLAGS]) +AC_SUBST([LIBNL_LIBS]) + + + + # Only COPYING.LIB is under version control, yet COPYING # is included as part of the distribution tarball. # Copy one to the other, but only if this is a srcdir-build. @@ -2183,6 +2202,11 @@ AC_MSG_NOTICE([ pcap: $LIBPCAP_CFLAGS else AC_MSG_NOTICE([ pcap: no]) fi +if test "$with_macvtap" = "yes" ; then +AC_MSG_NOTICE([ nl: $LIBNL_CFLAGS $LIBNL_LIBS]) +else +AC_MSG_NOTICE([ nl: no]) +fi AC_MSG_NOTICE([]) AC_MSG_NOTICE([Test suite]) AC_MSG_NOTICE([]) Index: libvirt-acl/libvirt.spec.in =================================================================== --- libvirt-acl.orig/libvirt.spec.in +++ libvirt-acl/libvirt.spec.in @@ -63,6 +63,7 @@ %define with_yajl 0%{!?_without_yajl:0} %define with_nwfilter 0%{!?_without_nwfilter:0} %define with_libpcap 0%{!?_without_libpcap:0} +%define with_macvtap 0%{!?_without_macvtap:0} # Non-server/HV driver defaults which are always enabled %define with_python 0%{!?_without_python:1} @@ -153,6 +154,11 @@ %if %{with_qemu} %define with_nwfilter 0%{!?_without_nwfilter:%{server_drivers}} %define with_libpcap 0%{!?_without_libpcap:%{server_drivers}} +%define with_macvtap 0%{!?_without_macvtap:%{server_drivers}} +%endif + +%if %{with_macvtap} +%define with_libnl 1 %endif # Force QEMU to run as non-root @@ -282,6 +288,9 @@ BuildRequires: yajl-devel %if %{with_libpcap} BuildRequires: libpcap-devel %endif +%if %{with_libnl} +BuildRequires: libnl-devel +%endif %if %{with_avahi} BuildRequires: avahi-devel %endif @@ -531,6 +540,10 @@ of recent versions of Linux (and other O %define _without_libpcap --without-libpcap %endif +%if ! %{with_macvtap} +%define _without_macvtap --without-macvtap +%endif + %configure %{?_without_xen} \ %{?_without_qemu} \ %{?_without_openvz} \ @@ -560,6 +573,7 @@ of recent versions of Linux (and other O %{?_without_udev} \ %{?_without_yajl} \ %{?_without_libpcap} \ + %{?_without_macvtap} \ --with-qemu-user=%{qemu_user} \ --with-qemu-group=%{qemu_group} \ --with-init-script=redhat \