On Fri, Sep 30, 2005 at 08:59:35PM +0200, Alexander Weber wrote:
> mppe_compress[1]: osize too small! (have: 1400 need: 1404)
>
> ppp is configured to require 128-bit encryption.
> Altering the MTU value in the pppd options file does not help. After
> reducing the MTU by four bytes the messages changes to:
>
> mppe_compress[1]: osize too small! (have: 1396 need: 1400)
>
> So it seems ppp wants 4 more bytes regardless of what the MTU is set to.
Let me add a little detail here. The "need" value printed by the kernel
is bogus. Have a look at the relevant source:
drivers/net/ppp/ppp_mppe.c:
| /* Make sure we have enough room to generate an encrypted packet. */
| if (osize < isize + MPPE_OVHD + 2) {
| /* Drop the packet if we should encrypt it, but can't. */
| printk(KERN_DEBUG "mppe_compress[%d]: osize too small! "
| "(have: %d need: %d)\n", state->unit,
| osize, osize + MPPE_OVHD + 2);
| return -1;
| }
You can see that the value printed as "need" is not the one being
compared. Instead it is always 4 greater than the "have" value
regardless of the actual isize given. You might need to lower the MTU
even further.
Helmut
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