[PATCH net-next-2.6] net: add limits to ip_default_ttl

[Eric Dumazet <eric.dumazet@gmail.com>]

Le lundi 13 décembre 2010 à 10:04 -0800, David Miller a écrit :
> Always go through a new ip4_dst_hoplimit() helper, just like ipv6.
> 
> This allowed several simplifications:
> 
> 1) The interim dst_metric_hoplimit() can go as it's no longer
>    userd.
> 
> 2) The sysctl_ip_default_ttl entry no longer needs to use
>    ipv4_doint_and_flush, since the sysctl is not cached in
>    routing cache metrics any longer.
> 
> 3) ipv4_doint_and_flush no longer needs to be exported and
>    therefore can be marked static.
> 
> When ipv4_doint_and_flush_strategy was removed some time ago,
> the external declaration in ip.h was mistakenly left around
> so kill that off too.
> 
> We have to move the sysctl_ip_default_ttl declaration into
> ipv4's route cache definition header net/route.h, because
> currently net/ip.h (where the declaration lives now) has
> a back dependency on net/route.h
> 
> Signed-off-by: David S. Miller <davem@davemloft.net>
> ---

> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -155,7 +155,7 @@ static struct ctl_table ipv4_table[] = {
>  		.data		= &sysctl_ip_default_ttl,
>  		.maxlen		= sizeof(int),
>  		.mode		= 0644,
> -		.proc_handler	= ipv4_doint_and_flush,
> +		.proc_handler	= proc_dointvec,
>  		.extra2		= &init_net,
>  	},

Please find following patch then, because extra2 is not anymore used.

BTW, I cant find where extra2 was set to actual struct net pointer in
net-2.6 kernel. I suspect a write on /proc/sys/net/ipv4/ip_default_ttl
was flushing routes of initial net only, not current one ?

I can see this extra2 param properly handled in
__devinet_sysctl_register() for /proc/net/ipv4/conf parameters, not for
ip_default_ttl.



For net-next-2.6, we could remove the line, or we could add sensible
limits ;)

[PATCH net-next-2.6] net: add limits to ip_default_ttl

ip_default_ttl should be between 1 and 255

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 net/ipv4/sysctl_net_ipv4.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index e85ff59..1a45665 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -28,6 +28,8 @@ static int ip_local_port_range_min[] = { 1, 1 };
 static int ip_local_port_range_max[] = { 65535, 65535 };
 static int tcp_adv_win_scale_min = -31;
 static int tcp_adv_win_scale_max = 31;
+static int ip_ttl_min = 1;
+static int ip_ttl_max = 255;
 
 /* Update system visible IP port range */
 static void set_local_port_range(int range[2])
@@ -155,8 +157,9 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &sysctl_ip_default_ttl,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-		.extra2		= &init_net,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &ip_ttl_min,
+		.extra2		= &ip_ttl_max,
 	},
 	{
 		.procname	= "ip_no_pmtu_disc",