[Babel-users] [PATCH] Add option to consider sysctl write failures as non-fatal.

[Jernej Kos]

Hello!

+1 for this patch. We are also running babeld in a Docker container and
this requires us to run it as a privileged container due to some Docker
deficiencies in setting network sysctls inside containers.


Jernej

On 10. 08. 2015 18:02, Toke Høiland-Jørgensen wrote:
> Babeld will exit with a fatal error if it is unable to write sysctls.
> When running in a container, however, /proc/sys may be mounted
> read-only, which causes babeld to fail.
> 
> This adds a switch to consider sysctl failures as non-fatal, in which
> case a warning will be issues rather than having the daemon fail to
> start.
> 
> Signed-off-by: Toke Høiland-Jørgensen <toke at toke.dk>
> ---
>  babeld.c         |  8 ++++++--
>  babeld.h         |  1 +
>  babeld.man       | 12 ++++++++++++
>  configuration.c  |  3 +++
>  kernel_netlink.c |  7 ++++++-
>  5 files changed, 28 insertions(+), 3 deletions(-)
> 
> diff --git a/babeld.c b/babeld.c
> index 943f042..45b14fa 100644
> --- a/babeld.c
> +++ b/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 sysctl_nonfatal = 0;
>  const char *logfile = NULL,
>      *pidfile = "/var/run/babeld.pid",
>      *state_file = "/var/lib/babel-state";
> @@ -128,7 +129,7 @@ main(int argc, char **argv)
>  
>      while(1) {
>          opt = getopt(argc, argv,
> -                     "m:p:h:H:i:k:A:srR:uS:d:g:lwz:M:t:T:c:C:DL:I:");
> +                     "m:p:h:H:i:k:A:srR:uS:d:g:lwz:M:t:T:c:C:DL:I:F");
>          if(opt < 0)
>              break;
>  
> @@ -263,6 +264,9 @@ main(int argc, char **argv)
>          case 'D':
>              do_daemonise = 1;
>              break;
> +	case 'F':
> +            sysctl_nonfatal = 1;
> +            break;
>          case 'L':
>              logfile = optarg;
>              break;
> @@ -800,7 +804,7 @@ main(int argc, char **argv)
>              "                "
>              "[-t table] [-T table] [-c file] [-C statement]\n"
>              "                "
> -            "[-d level] [-D] [-L logfile] [-I pidfile]\n"
> +            "[-d level] [-D] [-F] [-L logfile] [-I pidfile]\n"
>              "                "
>              "[id] interface...\n",
>              argv[0]);
> diff --git a/babeld.h b/babeld.h
> index 92ce9b5..c1f26fe 100644
> --- a/babeld.h
> +++ b/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 sysctl_nonfatal;
>  extern int do_daemonise;
>  extern const char *logfile, *pidfile, *state_file;
>  extern int link_detect;
> diff --git a/babeld.man b/babeld.man
> index ec600c2..7182f30 100644
> --- a/babeld.man
> +++ b/babeld.man
> @@ -135,6 +135,11 @@ Specify a configuration statement directly on the command line.
>  .B \-D
>  Daemonise at startup.
>  .TP
> +.B \-F
> +Don't consider failures writing to sysctl as fatal. Warn of the failures, but
> +continue running. This is useful when running babeld in a container that mounts
> +/proc/sys as read-only (as systemd-nspawn does, for instance).
> +.TP
>  .BI \-L " logfile"
>  Specify a file to log random ``how do you do?'' messages to.  This
>  defaults to standard error if not daemonising, and to
> @@ -253,6 +258,13 @@ This specifies whether to daemonize at startup, and is equivalent to
>  the command-line option
>  .BR \-D .
>  .TP
> +.BR sysctl-nonfatal " {" true | false }
> +This controls whether to consider failures writing to sysctl as fatal. If set,
> +warn of the failures, but continue running. This is useful when running babeld
> +in a container that mounts /proc/sys as read-only (as systemd-nspawn does, for
> +instance). Equivalent to the command line option
> +.BR \-F .
> +.TP
>  .BI state-file " filename"
>  This specifies the name of the file used for preserving long-term
>  information between invocations of the
> diff --git a/configuration.c b/configuration.c
> index 6a9c09d..571e220 100644
> --- a/configuration.c
> +++ b/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, "sysctl-nonfatal") == 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, "sysctl-nonfatal") == 0)
> +            sysctl_nonfatal = b;
>          else if(strcmp(token, "ipv6-subtrees") == 0)
>              has_ipv6_subtrees = b;
>          else if(strcmp(token, "reflect-kernel-metric") == 0)
> diff --git a/kernel_netlink.c b/kernel_netlink.c
> index ab63d33..0154c63 100644
> --- a/kernel_netlink.c
> +++ b/kernel_netlink.c
> @@ -183,8 +183,13 @@ write_proc(char *filename, int value)
>      n = snprintf(buf, 100, "%d", value);
>  
>      fd = open(filename, O_WRONLY);
> -    if(fd < 0)
> +    if(fd < 0 && sysctl_nonfatal) {
> +        fprintf(stderr, "Warning: writing sysctl %s failed (non-fatal): %s.\n",
> +                filename, strerror(errno));
> +        return 1;
> +    } else if(fd < 0) {
>          return -1;
> +    }
>  
>      rc = write(fd, buf, n);
>      if(rc < n) {
> 

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