sysctl: fix compatibility with procps sysctl

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)

Use procps syntax for output; for input, allow both.

function                                             old     new   delta
sysctl_dots_to_slashes                                86     143     +57
sysctl_act_on_setting                                443     453     +10
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 67/0)               Total: 67 bytes

Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 26 insertions, 2 deletions

diff --git a/procps/sysctl.c b/procps/sysctl.c
index 5303460f9..6d77185ca 100644
--- a/procps/sysctl.c
+++ b/procps/sysctl.c
@@ -56,9 +56,32 @@ enum {
 
 static void sysctl_dots_to_slashes(char *name)
 {
-        char *cptr, *last_good, *end;
+        char *cptr, *last_good, *end, *slash;
         char end_ch;
 
+        end = strchrnul(name, '=');
+
+        slash = strchrnul(name, '/');
+        if (slash < end
+         && strchrnul(name, '.') < slash
+        ) {
+                /* There are both dots and slashes, and 1st dot is
+                 * before 1st slash.
+                 * (IOW: not raw, unmangled a/b/c.d format)
+                 *
+                 * procps supports this syntax for names with dots:
+                 *  net.ipv4.conf.eth0/100.mc_forwarding
+                 * (dots and slashes are simply swapped)
+                 */
+                while (end != name) {
+                        end--;
+                        if (*end == '.') *end = '/';
+                        else if (*end == '/') *end = '.';
+                }
+                return;
+        }
+        /* else: use our old behavior: */
+
         /* Convert minimum number of '.' to '/' so that
          * we end up with existing file's name.
          *
@@ -77,7 +100,6 @@ static void sysctl_dots_to_slashes(char *name)
          *
          * To set up testing: modprobe 8021q; vconfig add eth0 100
          */
-        end = strchrnul(name, '=');
         end_ch = *end;
         *end = '.'; /* trick the loop into trying full name too */
 
@@ -114,6 +136,8 @@ static int sysctl_act_on_setting(char *setting)
         while (*cptr) {
                 if (*cptr == '/')
                         *cptr = '.';
+                else if (*cptr == '.')
+                        *cptr = '/';
                 cptr++;
         }