| /* |
| * 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; |
| } |