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platform: add a new function nmp_utils_open_sysctl()

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A race condition may happen when NetworkManager opens sysfs and udev
renames interface name at the same time. Thomas Haller provides a new
function [1] which can avoid the race condition when opening sysfs.

This patch is a direct copy from [1].

[1] https://mail.gnome.org/archives/networkmanager-list/2016-December/msg00004.html

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
This commit is contained in:
Kai-Heng Feng
2016-12-07 18:15:13 +08:00
committed by Thomas Haller
parent 99e1e4d6a1
commit 713c74f6e4
2 changed files with 52 additions and 0 deletions
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50
src/platform/nm-platform-utils.c
View File

@@ -31,6 +31,7 @@
#include <linux/mii.h>
#include <linux/version.h>
#include <linux/rtnetlink.h>
#include <fcntl.h>
#include "nm-utils.h"
#include "nm-setting-wired.h"
@@ -47,6 +48,7 @@
G_STMT_START { (pedata)->speed = (guint16) (speed); } G_STMT_END
#endif
extern char *if_indextoname (unsigned int __ifindex, char *__ifname);
static gboolean
ethtool_get (const char *name, gpointer edata)
@@ -623,3 +625,51 @@ nmp_utils_ip_config_source_to_string (NMIPConfigSource source, char *buf, gsize
return buf;
}
int
nmp_utils_open_sysctl(int ifindex, const char *ifname)
{
#define SYS_CLASS_NET "/sys/class/net/"
char ifname_buf[IFNAMSIZ];
guint try_count = 0;
char sysdir[NM_STRLEN (SYS_CLASS_NET) + IFNAMSIZ + 1] = SYS_CLASS_NET;
char fd_buf[256];
int fd;
int fd_ifindex;
ssize_t nn;
while (++try_count < 4) {
if (!ifname) {
ifname = if_indextoname (ifindex, ifname_buf);
if (!ifname)
return -1;
}
nm_utils_ifname_cpy (&sysdir[NM_STRLEN (SYS_CLASS_NET)], ifname);
fd = open (sysdir, O_DIRECTORY);
if (fd < 0)
goto next;
fd_ifindex = openat (fd, "ifindex", 0);
if (fd_ifindex < 0) {
close (fd);
goto next;
}
/* read ifindex file, and compare it to @ifindex. If match, return fd. */
nn = nm_utils_fd_read_loop (fd_ifindex, fd_buf, sizeof (fd_buf) - 1, FALSE);
if (nn < 0) {
close (fd);
close (fd_ifindex);
goto next;
}
fd_buf[sizeof (fd_buf) - 1] = '\0';
if (ifindex != _nm_utils_ascii_str_to_int64 (fd_buf, 10, 1, G_MAXINT, -1)) {
close (fd);
close (fd_ifindex);
goto next;
}
return fd;
next:
ifname = NULL;
}
return -1;
}

2
src/platform/nm-platform-utils.h
View File

@@ -61,4 +61,6 @@ NMIPConfigSource nmp_utils_ip_config_source_coerce_from_rtprot (NMIPConfigSource
NMIPConfigSource nmp_utils_ip_config_source_round_trip_rtprot (NMIPConfigSource source) _nm_const;
const char * nmp_utils_ip_config_source_to_string (NMIPConfigSource source, char *buf, gsize len);
int nmp_utils_open_sysctl(int ifindex, const char *ifname);
#endif /* __NM_PLATFORM_UTILS_H__ */