Here we go again. The changes are as follows:
1) the spaces are gone and now it is tabs.
2) used msecs_to_jiffies() and jiffies_to_msecs(). I'm much happier with 
  that. I didn't know those functions existed.
3) changed over to proc_doulongvec_ms_jiffies_minmax(). Last night's 
test compile failed because I was out of disk. I figured that the code I 
changed had compiled. I guess not.

I really didn't understand Yoshifuji Hideaki's comment. (sorry)

-ben


Vlad Yasevich wrote:
> Ben Woodard wrote:
>  ------------------------------------------------------------------------
>> diff -ru linux-2.6.18/include/net/tcp.h linux-2.6.18.new/include/net/tcp.h
>> --- linux-2.6.18/include/net/tcp.h	2006-09-19 20:42:06.000000000 -0700
>> +++ linux-2.6.18.new/include/net/tcp.h	2006-10-10 18:42:00.000000000 -0700
>> @@ -227,11 +227,23 @@
>>  extern int sysctl_tcp_base_mss;
>>  extern int sysctl_tcp_workaround_signed_windows;
>>  extern int sysctl_tcp_slow_start_after_idle;
>> +extern unsigned long sysctl_tcp_rto_max;
>> +extern unsigned long sysctl_tcp_rto_init;
>>  
>>  extern atomic_t tcp_memory_allocated;
>>  extern atomic_t tcp_sockets_allocated;
>>  extern int tcp_memory_pressure;
>>  
>> +static inline unsigned long tcp_rto_max(struct tcp_sock *tp)
>> +{
>> +        return tp->rto_max ? tp->rto_max*HZ/1000 : sysctl_tcp_rto_max;
>                                 ^^^^^^^^^^^^^^^^^^^
> That should probably be msecs_to_jiffies(tp->rto_max)
> 
>> +}
>> +
>> +static inline unsigned long tcp_rto_init(struct tcp_sock *tp)
>> +{
>> +        return tp->rto_init ? tp->rto_init*HZ/1000 : sysctl_tcp_rto_init;
> 
> Ditto.
> 
>> +}
>> +
>>  /*
>>   * The next routines deal with comparing 32 bit unsigned ints
>>   * and worry about wraparound (automatic with unsigned arithmetic).
>> diff -ru linux-2.6.18/net/ipv4/sysctl_net_ipv4.c linux-2.6.18.new/net/ipv4/sysctl_net_ipv4.c
>> --- linux-2.6.18/net/ipv4/sysctl_net_ipv4.c	2006-09-19 20:42:06.000000000 -0700
>> +++ linux-2.6.18.new/net/ipv4/sysctl_net_ipv4.c	2006-10-10 16:32:08.000000000 -0700
>> @@ -128,6 +128,8 @@
>>  	return ret;
>>  }
>>  
>> +static unsigned long tcp_rto_min=0;
>> +static unsigned long tcp_rto_max=65535;
>>  
>>  ctl_table ipv4_table[] = {
>>          {
>> @@ -697,6 +699,26 @@
>>  		.mode		= 0644,
>>  		.proc_handler	= &proc_dointvec
>>  	},
>> +	{
>> +	        .ctl_name       = NET_TCP_RTO_MAX,
>> +		.procname       = "tcp_rto_max",
>> +		.data           = &sysctl_tcp_rto_max,
>> +		.maxlen         = sizeof(unsigned),
>> +		.mode           = 0644,
>> +		.proc_handler   = &proc_doulongvec_ms_jiffies,
>> +		.extra1         = &tcp_rto_min_constant,
>> +		.extra2         = &tcp_rto_max_constant,
>> +	},
>> +	{
>> +	        .ctl_name       = NET_TCP_RTO_INIT,
>> +		.procname       = "tcp_rto_init",
>> +		.data           = &sysctl_tcp_rto_init,
>> +		.maxlen         = sizeof(unsigned),
>> +		.mode           = 0644,
>> +		.proc_handler   = &proc_doulongvec_ms_jiffies,
>> +		.extra1         = &tcp_rto_min_constant,
>> +		.extra2         = &tcp_rto_max_constant,
>> +	},
>>  	{ .ctl_name = 0 }
>>  };
> 
> Try as I might, I can't find proc_doulongvec_ms_jiffies() anywhere.  I think
> you meant proc_doulongvec_ms_jiffies_minmax()?
> 
> Also, this function has a bug in that it doesn't do corrections for potentially different
> HZ values.  Look at the msecs_to_jiffies...  When I've used proc_doulongvec_ms_jiffies_minmax()
> before, I would seen rather interesting truncation errors such that sysctl input didn't match
> sysctl output.
> 
>>  
>> diff -ru linux-2.6.18/net/ipv4/tcp.c linux-2.6.18.new/net/ipv4/tcp.c
>> --- linux-2.6.18/net/ipv4/tcp.c	2006-09-19 20:42:06.000000000 -0700
>> +++ linux-2.6.18.new/net/ipv4/tcp.c	2006-10-10 18:37:40.000000000 -0700
>> @@ -1764,6 +1764,8 @@
>>  	return err;
>>  }
>>  
>> +#define TCP_BACKOFF_MAXVAL 65535
>> +
>>  /*
>>   *	Socket option code for TCP.
>>   */
>> @@ -1939,6 +1941,21 @@
>>  		}
>>  		break;
>>  
>> +        case TCP_BACKOFF_MAX:
>> +                if (val < 1 || val > TCP_BACKOFF_MAXVAL)
>> +                        err = -EINVAL;
>> +                else
>> +                        tp->rto_max = val;
>> +                break;
>> + 
>> +        case TCP_BACKOFF_INIT:
>> +                if (val < 1 || val > TCP_BACKOFF_MAXVAL)
>> +                        err = -EINVAL;
>> +                else
>> +                        tp->rto_init = val;
>> +                break;
>> + 
>> + 
>>  	default:
>>  		err = -ENOPROTOOPT;
>>  		break;
>> @@ -2110,6 +2127,12 @@
>>  		if (copy_to_user(optval, icsk->icsk_ca_ops->name, len))
>>  			return -EFAULT;
>>  		return 0;
>> +        case TCP_BACKOFF_MAX:
>> +	        val = tcp_rto_max(tp)*1000/HZ;
>> +                break;
>> +        case TCP_BACKOFF_INIT:
>> +	        val = tcp_rto_init(tp)*1000/HZ;
> 
> The two divisions above introduce truncation errors such the input doesn't
> match the output.  Better to use jiffies_to_msecs().
> 
> Regards
> -vlad