From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:46943) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RBs6b-0001bT-Nt for qemu-devel@nongnu.org; Thu, 06 Oct 2011 13:51:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RBs6Z-0005rc-KZ for qemu-devel@nongnu.org; Thu, 06 Oct 2011 13:51:37 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:53194) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RBs6Z-0005rY-8w for qemu-devel@nongnu.org; Thu, 06 Oct 2011 13:51:35 -0400 Received: from /spool/local by us.ibm.com with XMail ESMTP for from ; Thu, 6 Oct 2011 11:51:14 -0600 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay01.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p96HnhCw059178 for ; Thu, 6 Oct 2011 11:49:43 -0600 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p96Hngcp024165 for ; Thu, 6 Oct 2011 11:49:43 -0600 Message-ID: <4E8DEA34.1050005@us.ibm.com> Date: Thu, 06 Oct 2011 12:49:40 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <1317915508-15491-1-git-send-email-rmarwah@linux.vnet.ibm.com> <1317915508-15491-5-git-send-email-rmarwah@linux.vnet.ibm.com> In-Reply-To: <1317915508-15491-5-git-send-email-rmarwah@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/4] Add support for bridge List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richa Marwaha Cc: coreyb@linux.vnet.ibm.com, qemu-devel@nongnu.org On 10/06/2011 10:38 AM, Richa Marwaha wrote: > The most common use of -net tap is to connect a tap device to a bridge. This > requires the use of a script and running qemu as root in order to allocate a > tap device to pass to the script. > > This model is great for portability and flexibility but it's incredibly > difficult to eliminate the need to run qemu as root. The only really viable > mechanism is to use tunctl to create a tap device, attach it to a bridge as > root, and then hand that tap device to qemu. The problem with this mechanism > is that it requires administrator intervention whenever a user wants to create > a guest. > > By essentially writing a helper that implements the most common qemu-ifup > script that can be safely given cap_net_admin, we can dramatically simplify > things for non-privileged users. We still support existing -net tap options > as a mechanism for advanced users and backwards compatibility. > > Currently, this is very Linux centric but there's really no reason why it > couldn't be extended for other Unixes. > > The default bridge that we attach to is qemubr0. The thinking is that a distro > could preconfigure such an interface to allow out-of-the-box bridged networking. > > Alternatively, if a user wants to use a different bridge, they can say: > > qemu-hda linux.img -net tap,br=br0,helper=/usr/local/libexec/qemu-bridge-helper > -net nic,model=virtio Wouldn't it be better to make the syntax: -net bridge[,br=BRIDGE][,helper=HELPER] And default BRIDGE to br0 and HELPER to ${prefix}/libexec/qemu-bridge-helper ? That gives distros a proper way to configure a default bridge making -net bridge Just Work for most people. Regards, Anthony Liguori > > Signed-off-by: Richa Marwaha > --- > configure | 2 + > net.c | 8 +++ > net.h | 2 + > net/tap.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++++++++--- > qemu-options.hx | 48 +++++++++++++----- > 5 files changed, 190 insertions(+), 20 deletions(-) > > diff --git a/configure b/configure > index f46e9b7..ef05954 100755 > --- a/configure > +++ b/configure > @@ -2775,6 +2775,8 @@ echo "sysconfdir=$sysconfdir">> $config_host_mak > echo "docdir=$docdir">> $config_host_mak > echo "libexecdir=\${prefix}/libexec">> $config_host_mak > echo "confdir=$confdir">> $config_host_mak > +echo "CONFIG_QEMU_SHAREDIR=\"$prefix$datasuffix\"">> $config_host_mak > +echo "CONFIG_QEMU_HELPERDIR=\"$prefix/libexec\"">> $config_host_mak > > case "$cpu" in > i386|x86_64|alpha|cris|hppa|ia64|lm32|m68k|microblaze|mips|mips64|ppc|ppc64|s390|s390x|sparc|sparc64|unicore32) > diff --git a/net.c b/net.c > index d05930c..4c3c551 100644 > --- a/net.c > +++ b/net.c > @@ -956,6 +956,14 @@ static const struct { > .type = QEMU_OPT_STRING, > .help = "script to shut down the interface", > }, { > + .name = "br", > + .type = QEMU_OPT_STRING, > + .help = "bridge name", > + }, { > + .name = "helper", > + .type = QEMU_OPT_STRING, > + .help = "command to execute to configure bridge", > + }, { > .name = "sndbuf", > .type = QEMU_OPT_SIZE, > .help = "send buffer limit" > diff --git a/net.h b/net.h > index 9f633f8..eeb19a7 100644 > --- a/net.h > +++ b/net.h > @@ -174,6 +174,8 @@ int do_netdev_del(Monitor *mon, const QDict *qdict, QObject **ret_data); > > #define DEFAULT_NETWORK_SCRIPT "/etc/qemu-ifup" > #define DEFAULT_NETWORK_DOWN_SCRIPT "/etc/qemu-ifdown" > +#define DEFAULT_BRIDGE_HELPER CONFIG_QEMU_HELPERDIR "/qemu-bridge-helper" > +#define DEFAULT_BRIDGE_INTERFACE "qemubr0" > > void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd); > > diff --git a/net/tap.c b/net/tap.c > index 1f26dc9..74f103a 100644 > --- a/net/tap.c > +++ b/net/tap.c > @@ -388,6 +388,108 @@ static int launch_script(const char *setup_script, const char *ifname, int fd) > return -1; > } > > +static int recv_fd(int c) > +{ > + int fd; > + uint8_t msgbuf[CMSG_SPACE(sizeof(fd))]; > + struct msghdr msg = { > + .msg_control = msgbuf, > + .msg_controllen = sizeof(msgbuf), > + }; > + struct cmsghdr *cmsg; > + struct iovec iov; > + uint8_t req[1]; > + ssize_t len; > + > + cmsg = CMSG_FIRSTHDR(&msg); > + cmsg->cmsg_level = SOL_SOCKET; > + cmsg->cmsg_type = SCM_RIGHTS; > + cmsg->cmsg_len = CMSG_LEN(sizeof(fd)); > + msg.msg_controllen = cmsg->cmsg_len; > + > + iov.iov_base = req; > + iov.iov_len = sizeof(req); > + > + msg.msg_iov =&iov; > + msg.msg_iovlen = 1; > + > + len = recvmsg(c,&msg, 0); > + if (len> 0) { > + memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd)); > + return fd; > + } > + > + return len; > +} > + > +static int net_bridge_run_helper(const char *helper, const char *bridge) > +{ > + sigset_t oldmask, mask; > + int pid, status; > + char *args[5]; > + char **parg; > + int sv[2]; > + > + sigemptyset(&mask); > + sigaddset(&mask, SIGCHLD); > + sigprocmask(SIG_BLOCK,&mask,&oldmask); > + > + if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1) { > + return -1; > + } > + > + /* try to launch bridge helper */ > + pid = fork(); > + if (pid == 0) { > + int open_max = sysconf(_SC_OPEN_MAX), i; > + char buf[32]; > + > + snprintf(buf, sizeof(buf), "%d", sv[1]); > + > + for (i = 0; i< open_max; i++) { > + if (i != STDIN_FILENO&& > + i != STDOUT_FILENO&& > + i != STDERR_FILENO&& > + i != sv[1]) { > + close(i); > + } > + } > + parg = args; > + *parg++ = (char *)helper; > + *parg++ = (char *)"--use-vnet"; > + *parg++ = (char *)bridge; > + *parg++ = buf; > + *parg++ = NULL; > + execv(helper, args); > + _exit(1); > + } else if (pid> 0) { > + int fd; > + > + close(sv[1]); > + > + do { > + fd = recv_fd(sv[0]); > + } while (fd == -1&& errno == EINTR); > + > + close(sv[0]); > + > + while (waitpid(pid,&status, 0) != pid) { > + /* loop */ > + } > + sigprocmask(SIG_SETMASK,&oldmask, NULL); > + if (fd< 0) { > + fprintf(stderr, "failed to recv file descriptor\n"); > + return -1; > + } > + > + if (WIFEXITED(status)&& WEXITSTATUS(status) == 0) { > + return fd; > + } > + } > + fprintf(stderr, "failed to launch bridge helper\n"); > + return -1; > +} > + > static int net_tap_init(QemuOpts *opts, int *vnet_hdr) > { > int fd, vnet_hdr_required; > @@ -433,8 +535,11 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan > if (qemu_opt_get(opts, "ifname") || > qemu_opt_get(opts, "script") || > qemu_opt_get(opts, "downscript") || > - qemu_opt_get(opts, "vnet_hdr")) { > - error_report("ifname=, script=, downscript= and vnet_hdr= is invalid with fd="); > + qemu_opt_get(opts, "vnet_hdr") || > + qemu_opt_get(opts, "br") || > + qemu_opt_get(opts, "helper")) { > + error_report("ifname=, script=, downscript=, vnet_hdr=," > + "br= and helper= are invalid with fd="); > return -1; > } > > @@ -446,6 +551,37 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan > fcntl(fd, F_SETFL, O_NONBLOCK); > > vnet_hdr = tap_probe_vnet_hdr(fd); > + } else if (qemu_opt_get(opts, "helper")) { > + if (qemu_opt_get(opts, "ifname") || > + qemu_opt_get(opts, "script") || > + qemu_opt_get(opts, "downscript")) { > + error_report("ifname=, script= and downscript=" > + "are invalid with helper="); > + return -1; > + } > + > + if (!qemu_opt_get(opts, "br")) { > + qemu_opt_set(opts, "br", DEFAULT_BRIDGE_INTERFACE); > + } > + > + fd = net_bridge_run_helper(qemu_opt_get(opts, "helper"), > + qemu_opt_get(opts, "br")); > + > + fcntl(fd, F_SETFL, O_NONBLOCK); > + > + vnet_hdr = tap_probe_vnet_hdr(fd); > + > + s = net_tap_fd_init(vlan, "bridge", name, fd, vnet_hdr); > + > + if (!s) { > + close(fd); > + return -1; > + } > + > + snprintf(s->nc.info_str, sizeof(s->nc.info_str), > + "br=%s", qemu_opt_get(opts, "br")); > + > + return 0; > } else { > if (!qemu_opt_get(opts, "script")) { > qemu_opt_set(opts, "script", DEFAULT_NETWORK_SCRIPT); > @@ -459,12 +595,12 @@ int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan > if (fd == -1) { > return -1; > } > - } > > - s = net_tap_fd_init(vlan, "tap", name, fd, vnet_hdr); > - if (!s) { > - close(fd); > - return -1; > + s = net_tap_fd_init(vlan, "tap", name, fd, vnet_hdr); > + if (!s) { > + close(fd); > + return -1; > + } > } > > if (tap_set_sndbuf(s->fd, opts)< 0) { > diff --git a/qemu-options.hx b/qemu-options.hx > index dfbabd0..ad4afa9 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -1149,11 +1149,15 @@ DEF("net", HAS_ARG, QEMU_OPTION_net, > "-net tap[,vlan=n][,name=str],ifname=name\n" > " connect the host TAP network interface to VLAN 'n'\n" > #else > - "-net tap[,vlan=n][,name=str][,fd=h][,ifname=name][,script=file][,downscript=dfile][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off][,vhostfd=h][,vhostforce=on|off]\n" > - " connect the host TAP network interface to VLAN 'n' and use the\n" > - " network scripts 'file' (default=" DEFAULT_NETWORK_SCRIPT ")\n" > - " and 'dfile' (default=" DEFAULT_NETWORK_DOWN_SCRIPT ")\n" > + "-net tap[,vlan=n][,name=str][,fd=h][,ifname=name][,script=file][,downscript=dfile][,br=bridge][,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off][,vhostfd=h][,vhostforce=on|off]\n" > + " connect the host TAP network interface to VLAN 'n' \n" > + " use network scripts 'file' (default=" DEFAULT_NETWORK_SCRIPT ")\n" > + " to configure it and 'dfile' (default=" DEFAULT_NETWORK_DOWN_SCRIPT ")\n" > + " to deconfigure it. This requires root privilege.\n" > " use '[down]script=no' to disable script execution\n" > + " use network helper 'helper' (default=" DEFAULT_BRIDGE_HELPER ") and\n" > + " use bridge 'br' (default=" DEFAULT_BRIDGE_INTERFACE ") to configure it. This\n" > + " does not require root privilege.\n" > " use 'fd=h' to connect to an already opened TAP interface\n" > " use 'sndbuf=nbytes' to limit the size of the send buffer (the\n" > " default is disabled 'sndbuf=0' to enable flow control set 'sndbuf=1048576')\n" > @@ -1322,26 +1326,44 @@ processed and applied to -net user. Mixing them with the new configuration > syntax gives undefined results. Their use for new applications is discouraged > as they will be removed from future versions. > > -@item -net tap[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}][,ifname=@var{name}] [,script=@var{file}][,downscript=@var{dfile}] > -Connect the host TAP network interface @var{name} to VLAN @var{n}, use > -the network script @var{file} to configure it and the network script > +@item -net tap[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}][,ifname=@var{name}] [,script=@var{file}][,downscript=@var{dfile}][,br=@var{bridge}][,helper=@var{helper}] > +Connect the host TAP network interface @var{name} to VLAN @var{n}. > + > +Use the network script @var{file} to configure it and the network script > @var{dfile} to deconfigure it. If @var{name} is not provided, the OS > -automatically provides one. @option{fd}=@var{h} can be used to specify > -the handle of an already opened host TAP interface. The default network > -configure script is @file{/etc/qemu-ifup} and the default network > -deconfigure script is @file{/etc/qemu-ifdown}. Use @option{script=no} > -or @option{downscript=no} to disable script execution. Example: > +automatically provides one. The default network configure script is > +@file{/etc/qemu-ifup} and the default network deconfigure script is > +@file{/etc/qemu-ifdown}. Use @option{script=no} or @option{downscript=no} > +to disable script execution. > + > +If running QEMU as an unprivileged user, use the network helper > +@var{helper} to configure the TAP interface. The default network > +bridge helper executable is @file{/usr/local/libexec/qemu-bridge-helper} > +and bridge name interface is @file{qemubr0}. > + > +@option{fd}=@var{h} can be used to specify the handle of an already > +opened host TAP interface. > + > +Examples: > > @example > +#launch a QEMU instance with the default network script > qemu linux.img -net nic -net tap > @end example > > -More complicated example (two NICs, each one connected to a TAP device) > @example > +#launch a QEMU instance with two NICs, each one connected > +#to a TAP device > qemu linux.img -net nic,vlan=0 -net tap,vlan=0,ifname=tap0 \ > -net nic,vlan=1 -net tap,vlan=1,ifname=tap1 > @end example > > +@example > +#launch a QEMU instance with the default network helper to > +#connect a TAP device to bridge br0 > +qemu linux.img -net nic -net tap,helper=/usr/local/libexec/qemu-bridge-helper,br=br0 > +@end example > + > @item -net socket[,vlan=@var{n}][,name=@var{name}][,fd=@var{h}] [,listen=[@var{host}]:@var{port}][,connect=@var{host}:@var{port}] > > Connect the VLAN @var{n} to a remote VLAN in another QEMU virtual