#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/if_link.h>
+
+#ifdef INET6
+#include <linux/if_addr.h>
+#endif
+
/* Attempt at retaining compile-support with older than 4.7 kernels, or kernels
* where RTM_NEWSTATS isn't defined for whatever reason.
*/
#define IFLA_STATS_LINK_64 1
#endif
-#ifdef INET6
-#include <linux/if_addr.h>
/* glibc versions prior to 2.24 do not define SOL_NETLINK */
#ifndef SOL_NETLINK
#define SOL_NETLINK 270
#endif
+
/* linux kernel versions prior to 4.3 do not define/support NETLINK_CAP_ACK */
#ifndef NETLINK_CAP_ACK
#define NETLINK_CAP_ACK 10
#endif
+
+/* linux kernel versions prior to 4.7 do not define/support IFLA_PPP_DEV_FD */
+#ifndef IFLA_PPP_MAX
+/* IFLA_PPP_DEV_FD is declared as enum when IFLA_PPP_MAX is defined */
+#define IFLA_PPP_DEV_FD 1
#endif
#include "pppd.h"
}
}
+/*
+ * make_ppp_unit_rtnetlink - register a new ppp network interface for ppp_dev_fd
+ * with specified req_ifname via rtnetlink. Interface name req_ifname must not
+ * be empty. Custom ppp unit id req_unit is ignored and kernel choose some free.
+ */
+static int make_ppp_unit_rtnetlink(void)
+{
+ struct {
+ struct nlmsghdr nlh;
+ struct ifinfomsg ifm;
+ struct {
+ struct rtattr rta;
+ char ifname[IFNAMSIZ];
+ } ifn;
+ struct {
+ struct rtattr rta;
+ struct {
+ struct rtattr rta;
+ char ifkind[sizeof("ppp")];
+ } ifik;
+ struct {
+ struct rtattr rta;
+ struct {
+ struct rtattr rta;
+ union {
+ int ppp_dev_fd;
+ } ppp;
+ } ifdata[1];
+ } ifid;
+ } ifli;
+ } nlreq;
+ struct {
+ struct nlmsghdr nlh;
+ struct nlmsgerr nlerr;
+ } nlresp;
+ struct sockaddr_nl nladdr;
+ struct iovec iov;
+ struct msghdr msg;
+ ssize_t nlresplen;
+ int one;
+ int fd;
+
+ fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+ if (fd < 0) {
+ error("make_ppp_unit_rtnetlink: socket(NETLINK_ROUTE): %m (line %d)", __LINE__);
+ return 0;
+ }
+
+ /* Tell kernel to not send to us payload of acknowledgment error message. */
+ one = 1;
+ setsockopt(fd, SOL_NETLINK, NETLINK_CAP_ACK, &one, sizeof(one));
+
+ memset(&nladdr, 0, sizeof(nladdr));
+ nladdr.nl_family = AF_NETLINK;
+
+ if (bind(fd, (struct sockaddr *)&nladdr, sizeof(nladdr)) < 0) {
+ error("make_ppp_unit_rtnetlink: bind(AF_NETLINK): %m (line %d)", __LINE__);
+ close(fd);
+ return 0;
+ }
+
+ memset(&nlreq, 0, sizeof(nlreq));
+ nlreq.nlh.nlmsg_len = sizeof(nlreq);
+ nlreq.nlh.nlmsg_type = RTM_NEWLINK;
+ nlreq.nlh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | NLM_F_EXCL | NLM_F_CREATE;
+ nlreq.ifm.ifi_family = AF_UNSPEC;
+ nlreq.ifm.ifi_type = ARPHRD_NETROM;
+ nlreq.ifn.rta.rta_len = sizeof(nlreq.ifn);
+ nlreq.ifn.rta.rta_type = IFLA_IFNAME;
+ strlcpy(nlreq.ifn.ifname, req_ifname, sizeof(nlreq.ifn.ifname));
+ nlreq.ifli.rta.rta_len = sizeof(nlreq.ifli);
+ nlreq.ifli.rta.rta_type = IFLA_LINKINFO;
+ nlreq.ifli.ifik.rta.rta_len = sizeof(nlreq.ifli.ifik);
+ nlreq.ifli.ifik.rta.rta_type = IFLA_INFO_KIND;
+ strcpy(nlreq.ifli.ifik.ifkind, "ppp");
+ nlreq.ifli.ifid.rta.rta_len = sizeof(nlreq.ifli.ifid);
+ nlreq.ifli.ifid.rta.rta_type = IFLA_INFO_DATA;
+ nlreq.ifli.ifid.ifdata[0].rta.rta_len = sizeof(nlreq.ifli.ifid.ifdata[0]);
+ nlreq.ifli.ifid.ifdata[0].rta.rta_type = IFLA_PPP_DEV_FD;
+ nlreq.ifli.ifid.ifdata[0].ppp.ppp_dev_fd = ppp_dev_fd;
+
+ memset(&nladdr, 0, sizeof(nladdr));
+ nladdr.nl_family = AF_NETLINK;
+
+ memset(&iov, 0, sizeof(iov));
+ iov.iov_base = &nlreq;
+ iov.iov_len = sizeof(nlreq);
+
+ memset(&msg, 0, sizeof(msg));
+ msg.msg_name = &nladdr;
+ msg.msg_namelen = sizeof(nladdr);
+ msg.msg_iov = &iov;
+ msg.msg_iovlen = 1;
+
+ if (sendmsg(fd, &msg, 0) < 0) {
+ error("make_ppp_unit_rtnetlink: sendmsg(RTM_NEWLINK/NLM_F_CREATE): %m (line %d)", __LINE__);
+ close(fd);
+ return 0;
+ }
+
+ memset(&iov, 0, sizeof(iov));
+ iov.iov_base = &nlresp;
+ iov.iov_len = sizeof(nlresp);
+
+ memset(&msg, 0, sizeof(msg));
+ msg.msg_name = &nladdr;
+ msg.msg_namelen = sizeof(nladdr);
+ msg.msg_iov = &iov;
+ msg.msg_iovlen = 1;
+
+ nlresplen = recvmsg(fd, &msg, 0);
+
+ if (nlresplen < 0) {
+ error("make_ppp_unit_rtnetlink: recvmsg(NLM_F_ACK): %m (line %d)", __LINE__);
+ close(fd);
+ return 0;
+ }
+
+ close(fd);
+
+ if (nladdr.nl_family != AF_NETLINK) {
+ error("make_ppp_unit_rtnetlink: recvmsg(NLM_F_ACK): Not a netlink packet (line %d)", __LINE__);
+ return 0;
+ }
+
+ if ((size_t)nlresplen < sizeof(nlresp) || nlresp.nlh.nlmsg_len < sizeof(nlresp)) {
+ error("make_ppp_unit_rtnetlink: recvmsg(NLM_F_ACK): Acknowledgment netlink packet too short (line %d)", __LINE__);
+ return 0;
+ }
+
+ /* acknowledgment packet for NLM_F_ACK is NLMSG_ERROR */
+ if (nlresp.nlh.nlmsg_type != NLMSG_ERROR) {
+ error("make_ppp_unit_rtnetlink: recvmsg(NLM_F_ACK): Not an acknowledgment netlink packet (line %d)", __LINE__);
+ return 0;
+ }
+
+ /* error == 0 indicates success, negative value is errno code */
+ if (nlresp.nlerr.error != 0) {
+ /*
+ * Linux kernel versions prior to 4.7 do not support creating ppp
+ * interfaces via rtnetlink API and therefore error response is
+ * expected. On older kernel versions do not show this error message.
+ * When error is different than EEXIST then pppd tries to fallback to
+ * the old ioctl method.
+ */
+ errno = (nlresp.nlerr.error < 0) ? -nlresp.nlerr.error : EINVAL;
+ if (kernel_version >= KVERSION(4,7,0))
+ error("Couldn't create ppp interface %s: %m", req_ifname);
+ return 0;
+ }
+
+ return 1;
+}
+
/*
* make_ppp_unit - make a new ppp unit for ppp_dev_fd.
* Assumes new_style_driver.
|| fcntl(ppp_dev_fd, F_SETFL, flags | O_NONBLOCK) == -1)
warn("Couldn't set /dev/ppp to nonblock: %m");
+ /*
+ * Via rtnetlink it is possible to create ppp network interface with
+ * custom ifname atomically. But it is not possible to specify custom
+ * ppp unit id.
+ *
+ * Tools like systemd, udev or NetworkManager are trying to query
+ * interface attributes based on interface name immediately when new
+ * network interface is created. And therefore immediate interface
+ * renaming is causing issues.
+ *
+ * So use rtnetlink API only when user requested custom ifname. It will
+ * avoid system issues with interface renaming.
+ */
+ if (req_unit == -1 && req_ifname[0] != '\0' && kernel_version >= KVERSION(2,1,16)) {
+ if (make_ppp_unit_rtnetlink()) {
+ if (ioctl(ppp_dev_fd, PPPIOCGUNIT, &ifunit))
+ fatal("Couldn't retrieve PPP unit id: %m");
+ return 0;
+ }
+ /*
+ * If interface with requested name already exist return error
+ * otherwise fallback to old ioctl method.
+ */
+ if (errno == EEXIST)
+ return -1;
+ }
+
ifunit = req_unit;
x = ioctl(ppp_dev_fd, PPPIOCNEWUNIT, &ifunit);
if (x < 0 && req_unit >= 0 && errno == EEXIST) {
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