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systemd/src/core/loopback-setup.c
Lennart Poettering 2c3ff76eb0 loopback: handle EPERM more gracefully
2012-04-13 18:52:53 +02:00

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9.1 KiB
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <sys/socket.h>
#include <net/if.h>
#include <asm/types.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include "util.h"
#include "macro.h"
#include "loopback-setup.h"
#include "socket-util.h"
#define NLMSG_TAIL(nmsg) \
((struct rtattr *) (((uint8_t*) (nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len)))
static int add_rtattr(struct nlmsghdr *n, size_t max_length, int type, const void *data, size_t data_length) {
size_t length;
struct rtattr *rta;
length = RTA_LENGTH(data_length);
if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(length) > max_length)
return -E2BIG;
rta = NLMSG_TAIL(n);
rta->rta_type = type;
rta->rta_len = length;
memcpy(RTA_DATA(rta), data, data_length);
n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(length);
return 0;
}
static ssize_t sendto_loop(int fd, const void *buf, size_t buf_len, int flags, const struct sockaddr *sa, socklen_t sa_len) {
for (;;) {
ssize_t l;
l = sendto(fd, buf, buf_len, flags, sa, sa_len);
if (l >= 0)
return l;
if (errno != EINTR)
return -errno;
}
}
static ssize_t recvfrom_loop(int fd, void *buf, size_t buf_len, int flags, struct sockaddr *sa, socklen_t *sa_len) {
for (;;) {
ssize_t l;
l = recvfrom(fd, buf, buf_len, flags, sa, sa_len);
if (l >= 0)
return l;
if (errno != EINTR)
return -errno;
}
}
static int add_adresses(int fd, int if_loopback, unsigned *requests) {
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 ifaddrmsg)) +
RTA_LENGTH(sizeof(struct in6_addr))];
} request;
struct ifaddrmsg *ifaddrmsg;
uint32_t ipv4_address = htonl(INADDR_LOOPBACK);
int r;
zero(request);
request.header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
request.header.nlmsg_type = RTM_NEWADDR;
request.header.nlmsg_flags = NLM_F_REQUEST|NLM_F_CREATE|NLM_F_ACK;
request.header.nlmsg_seq = *requests + 1;
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;
zero(sa);
sa.nl.nl_family = AF_NETLINK;
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;
union {
struct nlmsghdr header;
uint8_t buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
NLMSG_ALIGN(sizeof(struct ifinfomsg))];
} request;
struct ifinfomsg *ifinfomsg;
zero(request);
request.header.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
request.header.nlmsg_type = RTM_NEWLINK;
request.header.nlmsg_flags = NLM_F_REQUEST|NLM_F_ACK;
request.header.nlmsg_seq = *requests + 1;
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;
zero(sa);
sa.nl.nl_family = AF_NETLINK;
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, fd;
union {
struct sockaddr sa;
struct sockaddr_in in;
} sa;
/* 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;
zero(sa);
sa.in.sin_family = AF_INET;
sa.in.sin_addr.s_addr = INADDR_LOOPBACK;
if (bind(fd, &sa.sa, sizeof(sa.in)) >= 0)
r = 1;
else
r = errno == EADDRNOTAVAIL ? 0 : -errno;
close_nointr_nofail(fd);
return r;
}
int loopback_setup(void) {
int r, if_loopback;
union {
struct sockaddr sa;
struct sockaddr_nl nl;
} sa;
unsigned requests = 0, i;
int fd;
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;
zero(sa);
sa.nl.nl_family = AF_NETLINK;
if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
r = -errno;
goto finish;
}
r = add_adresses(fd, if_loopback, &requests);
if (r < 0)
goto finish;
r = start_interface(fd, if_loopback, &requests);
if (r < 0)
goto finish;
for (i = 0; i < requests; i++) {
r = read_response(fd, requests);
if (r == -EPERM)
eperm = true;
else if (r < 0)
goto finish;
}
if (eperm && check_loopback() < 0) {
r = -EPERM;
goto finish;
}
r = 0;
finish:
if (r < 0)
log_warning("Failed to configure loopback device: %s", strerror(-r));
if (fd >= 0)
close_nointr_nofail(fd);
return r;
}
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