[PATCH] sysctl: fix compatibility with procps sysctl

[Aaro Koskinen]

From: Aaro Koskinen <aaro.koskinen at nokia.com>

Busybox sysctl is incompatible with procps when '.' appears in
directory name, mostly happens with VLANs.

	busybox syntax (since 2008): net.ipv4.conf.eth0.100.mc_forwarding
	 procps syntax (since 2002): net.ipv4.conf.eth0/100.mc_forwarding
	         (supported by both: net/ipv4/conf/eth0.100/mc_forwarding)

Make procps syntax the default; for users relying on the old behaviour
provide a config option for time being.

Signed-off-by: Aaro Koskinen <aaro.koskinen at nokia.com>
---
 procps/sysctl.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/procps/sysctl.c b/procps/sysctl.c
index 5fa7646d1..3e79e3927 100644
--- a/procps/sysctl.c
+++ b/procps/sysctl.c
@@ -15,6 +15,23 @@
 //config:	default y
 //config:	help
 //config:	Configure kernel parameters at runtime.
+//config:config SYSCTL_OLDBUSYBOX_COMPAT
+//config:	bool "sysctl compatibility with older busybox versions"
+//config:	default n
+//config:	depends on BB_SYSCTL
+//config:	help
+//config:	Older busybox versions are incompatible with procps when
+//config:	handling VLAN interfaces. Busybox supported syntax:
+//config:		net.ipv4.conf.eth0.100.mc_forwarding
+//config:	while procps supports:
+//config:		net.ipv4.conf.eth0/100.mc_forwarding
+//config:
+//config:	Choose this option only if you are upgrading from an older
+//config:	busybox and need to maintain compatilibity e.g. for scripts
+//config:	that configure VLAN interfaces using sysctl. This option may be
+//config:	deprecated in the future so consider migrating to the procps
+//config:	syntax.
+//config:
 
 //applet:IF_BB_SYSCTL(APPLET_NOEXEC(sysctl, sysctl, BB_DIR_SBIN, BB_SUID_DROP, sysctl))
 
@@ -56,6 +73,7 @@ enum {
 
 static void sysctl_dots_to_slashes(char *name)
 {
+#ifdef CONFIG_SYSCTL_OLDBUSYBOX_COMPAT
 	char *cptr, *last_good, *end;
 
 	/* Convert minimum number of '.' to '/' so that
@@ -97,6 +115,25 @@ static void sysctl_dots_to_slashes(char *name)
 		cptr--;
 	}
 	*end = '\0';
+#else /* CONFIG_SYSCTL_OLDBUSYBOX_COMPAT */
+	char *cptr;
+	int n = 0;
+
+	cptr = name;
+	while (*cptr) {
+		if (*cptr == '.') {
+			*cptr = '/';
+			n++;
+		} else if (*cptr == '/') {
+			if (!n)
+				return; /* slash syntax is used */
+			*cptr = '.';
+		} else if (*cptr == '=') {
+			return;
+		}
+		cptr++;
+	}
+#endif /* CONFIG_SYSCTL_OLDBUSYBOX_COMPAT */
 }
 
 static int sysctl_act_on_setting(char *setting)
@@ -112,6 +149,10 @@ static int sysctl_act_on_setting(char *setting)
 	while (*cptr) {
 		if (*cptr == '/')
 			*cptr = '.';
+#ifndef CONFIG_SYSCTL_OLDBUSYBOX_COMPAT
+		else if (*cptr == '.')
+			*cptr = '/';
+#endif
 		cptr++;
 	}
 
-- 
2.17.0