Add configuration flag to skip initial kernel setup.

This adds a configuration flag to skip kernel (sysctl) setup on daemon
startup. This can be useful if running in, e.g., a container environment
where setting sysctls are not allowed.
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

babeld.c

@@ -67,6 +67,7 @@ int default_wired_hello_interval = -1;
 int resend_delay = -1;
 int random_id = 0;
 int do_daemonise = 0;
+int skip_kernel_setup = 0;
 const char *logfile = NULL,
     *pidfile = "/var/run/babeld.pid",
     *state_file = "/var/lib/babel-state";

babeld.h

@@ -86,6 +86,7 @@ extern time_t reboot_time;
 extern int default_wireless_hello_interval, default_wired_hello_interval;
 extern int resend_delay;
 extern int random_id;
+extern int skip_kernel_setup;
 extern int do_daemonise;
 extern const char *logfile, *pidfile, *state_file;
 extern int link_detect;

babeld.man

@@ -253,6 +253,11 @@ This specifies whether to daemonize at startup, and is equivalent to
 the command-line option
 .BR \-D .
 .TP
+.BR skip-kernel-setup " {" true | false }
+If this flag is set, no kernel (sysctl) setup is performed on startup. This can
+be useful when running in environments where system permissions prevent setting
+kernel parameters, for instance inside a Linux container.
+.TP
 .BI state-file " filename"
 This specifies the name of the file used for preserving long-term
 information between invocations of the

configuration.c

@@ -691,6 +691,7 @@ parse_option(int c, gnc_t gnc, void *closure, char *token)
               strcmp(token, "link-detect") == 0 ||
               strcmp(token, "random-id") == 0 ||
               strcmp(token, "daemonise") == 0 ||
+              strcmp(token, "skip-kernel-setup") == 0 ||
               strcmp(token, "ipv6-subtrees") == 0 ||
               strcmp(token, "reflect-kernel-metric") == 0) {
         int b;
@@ -706,6 +707,8 @@ parse_option(int c, gnc_t gnc, void *closure, char *token)
             random_id = b;
         else if(strcmp(token, "daemonise") == 0)
             do_daemonise = b;
+        else if(strcmp(token, "skip-kernel-setup") == 0)
+            skip_kernel_setup = b;
         else if(strcmp(token, "ipv6-subtrees") == 0)
             has_ipv6_subtrees = b;
         else if(strcmp(token, "reflect-kernel-metric") == 0)

kernel_netlink.c

@@ -514,6 +514,7 @@ kernel_setup(int setup)
         }
         nl_setup = 1;
 
+        if(skip_kernel_setup) return 1;
 
         for(i=0; i<NUM_SYSCTLS; i++) {
             s = &sysctl_settings[i];
@@ -541,6 +542,8 @@ kernel_setup(int setup)
         nl_command.sock = -1;
         nl_setup = 0;
 
+        if(skip_kernel_setup) return 1;
+
         for(i=0; i<NUM_SYSCTLS; i++) {
             s = &sysctl_settings[i];
             if(s->was && s->was != s->want) {

kernel_socket.c

@@ -214,6 +214,8 @@ kernel_setup(int setup)
     int mib[4];
     size_t datasize;
 
+    if(skip_kernel_setup) return 1;
+
     mib[0] = CTL_NET;
     mib[1] = AF_INET6;
     seq = time(NULL);