static int read_response(int fd, unsigned requests_max) {
union {
struct sockaddr sa;
struct sockaddr_nl nl;
} sa;
union {
struct nlmsghdr header;
uint8_t buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
NLMSG_ALIGN(sizeof(struct nlmsgerr))];
} response;
ssize_t l;
socklen_t sa_len = sizeof(sa);
struct nlmsgerr *nlmsgerr;
if ((l = recvfrom_loop(fd, &response, sizeof(response), 0, &sa.sa, &sa_len)) < 0)
return -errno;
if (sa_len != sizeof(sa.nl) ||
sa.nl.nl_family != AF_NETLINK)
return -EIO;
if (sa.nl.nl_pid != 0)
return 0;
if ((size_t) l < sizeof(struct nlmsghdr))
return -EIO;
if (response.header.nlmsg_type != NLMSG_ERROR ||
(pid_t) response.header.nlmsg_pid != getpid() ||
response.header.nlmsg_seq >= requests_max)
return 0;
if ((size_t) l < NLMSG_LENGTH(sizeof(struct nlmsgerr)) ||
response.header.nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
return -EIO;
nlmsgerr = NLMSG_DATA(&response.header);
if (nlmsgerr->error < 0 && nlmsgerr->error != -EEXIST) {
log_warning("Netlink failure for request %i: %s", response.header.nlmsg_seq, strerror(-nlmsgerr->error));
return nlmsgerr->error;
}
return response.header.nlmsg_seq;
}
static int add_adresses(int fd, int if_loopback, unsigned *requests) {
union {
struct sockaddr sa;
struct sockaddr_nl nl;
} sa = {
.nl.nl_family = AF_NETLINK,
};
union {
struct nlmsghdr header;
uint8_t buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
RTA_LENGTH(sizeof(struct in6_addr))];
} request = {
.header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg)),
.header.nlmsg_type = RTM_NEWADDR,
.header.nlmsg_flags = NLM_F_REQUEST|NLM_F_CREATE|NLM_F_ACK,
.header.nlmsg_seq = *requests + 1,
};
struct ifaddrmsg *ifaddrmsg;
uint32_t ipv4_address = htonl(INADDR_LOOPBACK);
int r;
ifaddrmsg = NLMSG_DATA(&request.header);
ifaddrmsg->ifa_family = AF_INET;
ifaddrmsg->ifa_prefixlen = 8;
ifaddrmsg->ifa_flags = IFA_F_PERMANENT;
ifaddrmsg->ifa_scope = RT_SCOPE_HOST;
ifaddrmsg->ifa_index = if_loopback;
r = add_rtattr(&request.header, sizeof(request), IFA_LOCAL,
&ipv4_address, sizeof(ipv4_address));
if (r < 0)
return r;
if (sendto_loop(fd, &request, request.header.nlmsg_len, 0, &sa.sa, sizeof(sa)) < 0)
return -errno;
(*requests)++;
if (!socket_ipv6_is_supported())
return 0;
request.header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
request.header.nlmsg_seq = *requests + 1;
ifaddrmsg->ifa_family = AF_INET6;
ifaddrmsg->ifa_prefixlen = 128;
r = add_rtattr(&request.header, sizeof(request), IFA_LOCAL,
&in6addr_loopback, sizeof(in6addr_loopback));
if (r < 0)
return r;
if (sendto_loop(fd, &request, request.header.nlmsg_len, 0, &sa.sa, sizeof(sa)) < 0)
return -errno;
(*requests)++;
return 0;
}
static int start_interface(int fd, int if_loopback, unsigned *requests) {
union {
struct sockaddr sa;
struct sockaddr_nl nl;
} sa = {
.nl.nl_family = AF_NETLINK,
};
union {
struct nlmsghdr header;
uint8_t buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
NLMSG_ALIGN(sizeof(struct ifinfomsg))];
} request = {
.header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
.header.nlmsg_type = RTM_NEWLINK,
.header.nlmsg_flags = NLM_F_REQUEST|NLM_F_ACK,
.header.nlmsg_seq = *requests + 1,
};
struct ifinfomsg *ifinfomsg;
ifinfomsg = NLMSG_DATA(&request.header);
ifinfomsg->ifi_family = AF_UNSPEC;
ifinfomsg->ifi_index = if_loopback;
ifinfomsg->ifi_flags = IFF_UP;
ifinfomsg->ifi_change = IFF_UP;
if (sendto_loop(fd, &request, request.header.nlmsg_len, 0, &sa.sa, sizeof(sa)) < 0)
return -errno;
(*requests)++;
return 0;
}
static int read_response(int fd, unsigned requests_max) {
union {
struct sockaddr sa;
struct sockaddr_nl nl;
} sa;
union {
struct nlmsghdr header;
uint8_t buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
NLMSG_ALIGN(sizeof(struct nlmsgerr))];
} response;
ssize_t l;
socklen_t sa_len = sizeof(sa);
struct nlmsgerr *nlmsgerr;
l = recvfrom_loop(fd, &response, sizeof(response), 0, &sa.sa, &sa_len);
if (l < 0)
return -errno;
if (sa_len != sizeof(sa.nl) ||
sa.nl.nl_family != AF_NETLINK)
return -EIO;
if (sa.nl.nl_pid != 0)
return 0;
if ((size_t) l < sizeof(struct nlmsghdr))
return -EIO;
if (response.header.nlmsg_type != NLMSG_ERROR ||
(pid_t) response.header.nlmsg_pid != getpid() ||
response.header.nlmsg_seq >= requests_max)
return 0;
if ((size_t) l < NLMSG_LENGTH(sizeof(struct nlmsgerr)) ||
response.header.nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
return -EIO;
nlmsgerr = NLMSG_DATA(&response.header);
if (nlmsgerr->error < 0 && nlmsgerr->error != -EEXIST)
return nlmsgerr->error;
return response.header.nlmsg_seq;
}
static int check_loopback(void) {
int r;
_cleanup_close_ int fd;
union {
struct sockaddr sa;
struct sockaddr_in in;
} sa = {
.in.sin_family = AF_INET,
.in.sin_addr.s_addr = INADDR_LOOPBACK,
};
/* If we failed to set up the loop back device, check whether
* it might already be set up */
fd = socket(AF_INET, SOCK_DGRAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0);
if (fd < 0)
return -errno;
if (bind(fd, &sa.sa, sizeof(sa.in)) >= 0)
r = 1;
else
r = errno == EADDRNOTAVAIL ? 0 : -errno;
return r;
}
int loopback_setup(void) {
int r, if_loopback;
union {
struct sockaddr sa;
struct sockaddr_nl nl;
} sa = {
.nl.nl_family = AF_NETLINK,
};
unsigned requests = 0, i;
_cleanup_close_ int fd = -1;
bool eperm = false;
errno = 0;
if_loopback = (int) if_nametoindex("lo");
if (if_loopback <= 0)
return errno ? -errno : -ENODEV;
fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
if (fd < 0)
return -errno;
if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
r = -errno;
goto error;
}
r = add_adresses(fd, if_loopback, &requests);
if (r < 0)
goto error;
r = start_interface(fd, if_loopback, &requests);
if (r < 0)
goto error;
for (i = 0; i < requests; i++) {
r = read_response(fd, requests);
if (r == -EPERM)
eperm = true;
else if (r < 0)
goto error;
}
if (eperm && check_loopback() < 0) {
r = -EPERM;
goto error;
}
return 0;
error:
log_warning("Failed to configure loopback device: %s", strerror(-r));
return r;
}