diff options
Diffstat (limited to 'src/qemu-bridge-helper.c')
| -rw-r--r-- | src/qemu-bridge-helper.c | 451 |
1 files changed, 451 insertions, 0 deletions
diff --git a/src/qemu-bridge-helper.c b/src/qemu-bridge-helper.c new file mode 100644 index 0000000..36eb3bc --- /dev/null +++ b/src/qemu-bridge-helper.c @@ -0,0 +1,451 @@ +/* + * QEMU Bridge Helper + * + * Copyright IBM, Corp. 2011 + * + * Authors: + * Anthony Liguori <aliguori@us.ibm.com> + * Richa Marwaha <rmarwah@linux.vnet.ibm.com> + * Corey Bryant <coreyb@linux.vnet.ibm.com> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + * + */ + +#include "config-host.h" + +#include <stdio.h> +#include <errno.h> +#include <fcntl.h> +#include <unistd.h> +#include <string.h> +#include <stdlib.h> +#include <stdbool.h> +#include <ctype.h> +#include <glib.h> + +#include <sys/types.h> +#include <sys/ioctl.h> +#include <sys/socket.h> +#include <sys/un.h> +#include <sys/prctl.h> + +#include <net/if.h> + +#include <linux/sockios.h> + +#ifndef SIOCBRADDIF +#include <linux/if_bridge.h> +#endif + +#include "qemu/queue.h" + +#include "net/tap-linux.h" + +#ifdef CONFIG_LIBCAP +#include <cap-ng.h> +#endif + +#define DEFAULT_ACL_FILE CONFIG_QEMU_CONFDIR "/bridge.conf" + +enum { + ACL_ALLOW = 0, + ACL_ALLOW_ALL, + ACL_DENY, + ACL_DENY_ALL, +}; + +typedef struct ACLRule { + int type; + char iface[IFNAMSIZ]; + QSIMPLEQ_ENTRY(ACLRule) entry; +} ACLRule; + +typedef QSIMPLEQ_HEAD(ACLList, ACLRule) ACLList; + +static void usage(void) +{ + fprintf(stderr, + "Usage: qemu-bridge-helper [--use-vnet] --br=bridge --fd=unixfd\n"); +} + +static int parse_acl_file(const char *filename, ACLList *acl_list) +{ + FILE *f; + char line[4096]; + ACLRule *acl_rule; + + f = fopen(filename, "r"); + if (f == NULL) { + return -1; + } + + while (fgets(line, sizeof(line), f) != NULL) { + char *ptr = line; + char *cmd, *arg, *argend; + + while (isspace(*ptr)) { + ptr++; + } + + /* skip comments and empty lines */ + if (*ptr == '#' || *ptr == 0) { + continue; + } + + cmd = ptr; + arg = strchr(cmd, ' '); + if (arg == NULL) { + arg = strchr(cmd, '\t'); + } + + if (arg == NULL) { + fprintf(stderr, "Invalid config line:\n %s\n", line); + fclose(f); + errno = EINVAL; + return -1; + } + + *arg = 0; + arg++; + while (isspace(*arg)) { + arg++; + } + + argend = arg + strlen(arg); + while (arg != argend && isspace(*(argend - 1))) { + argend--; + } + *argend = 0; + + if (strcmp(cmd, "deny") == 0) { + acl_rule = g_malloc(sizeof(*acl_rule)); + if (strcmp(arg, "all") == 0) { + acl_rule->type = ACL_DENY_ALL; + } else { + acl_rule->type = ACL_DENY; + snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg); + } + QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); + } else if (strcmp(cmd, "allow") == 0) { + acl_rule = g_malloc(sizeof(*acl_rule)); + if (strcmp(arg, "all") == 0) { + acl_rule->type = ACL_ALLOW_ALL; + } else { + acl_rule->type = ACL_ALLOW; + snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg); + } + QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); + } else if (strcmp(cmd, "include") == 0) { + /* ignore errors */ + parse_acl_file(arg, acl_list); + } else { + fprintf(stderr, "Unknown command `%s'\n", cmd); + fclose(f); + errno = EINVAL; + return -1; + } + } + + fclose(f); + + return 0; +} + +static bool has_vnet_hdr(int fd) +{ + unsigned int features = 0; + + if (ioctl(fd, TUNGETFEATURES, &features) == -1) { + return false; + } + + if (!(features & IFF_VNET_HDR)) { + return false; + } + + return true; +} + +static void prep_ifreq(struct ifreq *ifr, const char *ifname) +{ + memset(ifr, 0, sizeof(*ifr)); + snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname); +} + +static int send_fd(int c, int fd) +{ + char msgbuf[CMSG_SPACE(sizeof(fd))]; + struct msghdr msg = { + .msg_control = msgbuf, + .msg_controllen = sizeof(msgbuf), + }; + struct cmsghdr *cmsg; + struct iovec iov; + char req[1] = { 0x00 }; + + 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; + memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd)); + + return sendmsg(c, &msg, 0); +} + +#ifdef CONFIG_LIBCAP +static int drop_privileges(void) +{ + /* clear all capabilities */ + capng_clear(CAPNG_SELECT_BOTH); + + if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED, + CAP_NET_ADMIN) < 0) { + return -1; + } + + /* change to calling user's real uid and gid, retaining supplemental + * groups and CAP_NET_ADMIN */ + if (capng_change_id(getuid(), getgid(), CAPNG_CLEAR_BOUNDING)) { + return -1; + } + + return 0; +} +#endif + +int main(int argc, char **argv) +{ + struct ifreq ifr; +#ifndef SIOCBRADDIF + unsigned long ifargs[4]; +#endif + int ifindex; + int fd = -1, ctlfd = -1, unixfd = -1; + int use_vnet = 0; + int mtu; + const char *bridge = NULL; + char iface[IFNAMSIZ]; + int index; + ACLRule *acl_rule; + ACLList acl_list; + int access_allowed, access_denied; + int ret = EXIT_SUCCESS; + +#ifdef CONFIG_LIBCAP + /* if we're run from an suid binary, immediately drop privileges preserving + * cap_net_admin */ + if (geteuid() == 0 && getuid() != geteuid()) { + if (drop_privileges() == -1) { + fprintf(stderr, "failed to drop privileges\n"); + return 1; + } + } +#endif + + /* parse arguments */ + for (index = 1; index < argc; index++) { + if (strcmp(argv[index], "--use-vnet") == 0) { + use_vnet = 1; + } else if (strncmp(argv[index], "--br=", 5) == 0) { + bridge = &argv[index][5]; + } else if (strncmp(argv[index], "--fd=", 5) == 0) { + unixfd = atoi(&argv[index][5]); + } else { + usage(); + return EXIT_FAILURE; + } + } + + if (bridge == NULL || unixfd == -1) { + usage(); + return EXIT_FAILURE; + } + + /* parse default acl file */ + QSIMPLEQ_INIT(&acl_list); + if (parse_acl_file(DEFAULT_ACL_FILE, &acl_list) == -1) { + fprintf(stderr, "failed to parse default acl file `%s'\n", + DEFAULT_ACL_FILE); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* validate bridge against acl -- default policy is to deny + * according acl policy if we have a deny and allow both + * then deny should always win over allow + */ + access_allowed = 0; + access_denied = 0; + QSIMPLEQ_FOREACH(acl_rule, &acl_list, entry) { + switch (acl_rule->type) { + case ACL_ALLOW_ALL: + access_allowed = 1; + break; + case ACL_ALLOW: + if (strcmp(bridge, acl_rule->iface) == 0) { + access_allowed = 1; + } + break; + case ACL_DENY_ALL: + access_denied = 1; + break; + case ACL_DENY: + if (strcmp(bridge, acl_rule->iface) == 0) { + access_denied = 1; + } + break; + } + } + + if ((access_allowed == 0) || (access_denied == 1)) { + fprintf(stderr, "access denied by acl file\n"); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* open a socket to use to control the network interfaces */ + ctlfd = socket(AF_INET, SOCK_STREAM, 0); + if (ctlfd == -1) { + fprintf(stderr, "failed to open control socket: %s\n", strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* open the tap device */ + fd = open("/dev/net/tun", O_RDWR); + if (fd == -1) { + fprintf(stderr, "failed to open /dev/net/tun: %s\n", strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* request a tap device, disable PI, and add vnet header support if + * requested and it's available. */ + prep_ifreq(&ifr, "tap%d"); + ifr.ifr_flags = IFF_TAP|IFF_NO_PI; + if (use_vnet && has_vnet_hdr(fd)) { + ifr.ifr_flags |= IFF_VNET_HDR; + } + + if (ioctl(fd, TUNSETIFF, &ifr) == -1) { + fprintf(stderr, "failed to create tun device: %s\n", strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* save tap device name */ + snprintf(iface, sizeof(iface), "%s", ifr.ifr_name); + + /* get the mtu of the bridge */ + prep_ifreq(&ifr, bridge); + if (ioctl(ctlfd, SIOCGIFMTU, &ifr) == -1) { + fprintf(stderr, "failed to get mtu of bridge `%s': %s\n", + bridge, strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* save mtu */ + mtu = ifr.ifr_mtu; + + /* set the mtu of the interface based on the bridge */ + prep_ifreq(&ifr, iface); + ifr.ifr_mtu = mtu; + if (ioctl(ctlfd, SIOCSIFMTU, &ifr) == -1) { + fprintf(stderr, "failed to set mtu of device `%s' to %d: %s\n", + iface, mtu, strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* Linux uses the lowest enslaved MAC address as the MAC address of + * the bridge. Set MAC address to a high value so that it doesn't + * affect the MAC address of the bridge. + */ + if (ioctl(ctlfd, SIOCGIFHWADDR, &ifr) < 0) { + fprintf(stderr, "failed to get MAC address of device `%s': %s\n", + iface, strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + ifr.ifr_hwaddr.sa_data[0] = 0xFE; + if (ioctl(ctlfd, SIOCSIFHWADDR, &ifr) < 0) { + fprintf(stderr, "failed to set MAC address of device `%s': %s\n", + iface, strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* add the interface to the bridge */ + prep_ifreq(&ifr, bridge); + ifindex = if_nametoindex(iface); +#ifndef SIOCBRADDIF + ifargs[0] = BRCTL_ADD_IF; + ifargs[1] = ifindex; + ifargs[2] = 0; + ifargs[3] = 0; + ifr.ifr_data = (void *)ifargs; + ret = ioctl(ctlfd, SIOCDEVPRIVATE, &ifr); +#else + ifr.ifr_ifindex = ifindex; + ret = ioctl(ctlfd, SIOCBRADDIF, &ifr); +#endif + if (ret == -1) { + fprintf(stderr, "failed to add interface `%s' to bridge `%s': %s\n", + iface, bridge, strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* bring the interface up */ + prep_ifreq(&ifr, iface); + if (ioctl(ctlfd, SIOCGIFFLAGS, &ifr) == -1) { + fprintf(stderr, "failed to get interface flags for `%s': %s\n", + iface, strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + ifr.ifr_flags |= IFF_UP; + if (ioctl(ctlfd, SIOCSIFFLAGS, &ifr) == -1) { + fprintf(stderr, "failed to bring up interface `%s': %s\n", + iface, strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* write fd to the domain socket */ + if (send_fd(unixfd, fd) == -1) { + fprintf(stderr, "failed to write fd to unix socket: %s\n", + strerror(errno)); + ret = EXIT_FAILURE; + goto cleanup; + } + + /* ... */ + + /* profit! */ + +cleanup: + if (fd >= 0) { + close(fd); + } + if (ctlfd >= 0) { + close(ctlfd); + } + while ((acl_rule = QSIMPLEQ_FIRST(&acl_list)) != NULL) { + QSIMPLEQ_REMOVE_HEAD(&acl_list, entry); + g_free(acl_rule); + } + + return ret; +} |
