Is this a bug?

[Alexander Motin]

Hi!

Alexander Motin wrote:
> I have one strange problem with dummynet & IP fragmentation.
> 
> I have FreeBSD 4.8-RELEASE router with few interfaces:
> em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         options=3<rxcsum,txcsum>
>         inet 195.248.191.172 netmask 0xffffffc0 broadcast 195.248.191.191
>         ether 00:30:48:20:8e:7e
>         media: Ethernet autoselect (1000baseTX <full-duplex>)
>         status: active
> ng4: flags=88d1<UP,POINTOPOINT,RUNNING,NOARP,SIMPLEX,MULTICAST> mtu 1492
>         inet 195.248.191.172 --> 212.86.231.58 netmask 0xffffffff
> 
> Interface ng4 have MTU 1492 because it is PPPoE link.
> When I do not use dummynet on router and somebody send a big
> (>1492bytes) packet to 212.86.231.58 with DontFragment flag set router
> generates ICMP reply message (Fragmentation Needed). This is correct.
> 
> But when I use dummynet on that interface:
> 10170 pipe 10009 ip from any to any out xmit ng4
> 10175 allow ip from any to any via ng4
> 
> 10009: 128.000 Kbit/s    0 ms   50 sl. 1 queues (1 buckets) droptail
>     mask: 0x00 0x00000000/0x0000 -> 0x00000000/0x0000
> BKT Prot ___Source IP/port____ ____Dest. IP/port____ Tot_pkt/bytes
> Pkt/Byte Drp
>   0 udp   195.248.191.65/53      212.86.231.58/1118  50965 28380582  0
>    0 143
> 
> router stops sending that ICMP messages. Pipe is not overflowed at that
> tme, it is empty.

I recheck this on other router on Ethernet (rl0) interface.

When I set MTU 1400 on rl0 interface I could see generated ICMP messages:
20:27:23.660470 dp3-w-com.alkar.net.ftp-data > pc.mavhome.dp.ua.1100: . 
1027:2487(1460) ack 1 win 58400 (DF)
20:27:23.660580 router.mavhome.dp.ua > dp3-w-com.alkar.net: icmp: 
pc.mavhome.dp.ua unreachable - need to frag (mtu 1400) (DF)

But when I configure outgoing pipe on this interface:
ipfw pipe 2 config bw 64kbit/s
ipfw add 1000 pipe 2 all from any to any out via rl0
I got problem:
20:29:32.778561 DP6-W-CUS.alkar.net.4522 > pc.mavhome.dp.ua.1103: . 
1025:2485(1460) ack 1 win 58400 (DF)
20:29:35.080903 DP6-W-CUS.alkar.net.4522 > pc.mavhome.dp.ua.1103: . 
1025:2485(1460) ack 1 win 58400 (DF)
20:29:39.274113 DP6-W-CUS.alkar.net.4522 > pc.mavhome.dp.ua.1103: . 
1025:2485(1460) ack 1 win 58400 (DF)
20:29:47.306847 DP6-W-CUS.alkar.net.4522 > pc.mavhome.dp.ua.1103: . 
1025:2485(1460) ack 1 win 58400 (DF)

Hey, Developers! Where are you? Can anybody comment this?

-- 
Alexander Motin