Date: Thu, 22 Dec 2016 12:25:19 +0100 From: Harry Schmalzbauer <freebsd@omnilan.de> To: "Andrey V. Elsukov" <bu7cher@yandex.ru> Cc: freebsd-virtualization@freebsd.org Subject: Re: Jumbo frames truncated at 4084 bytes by virtio-net? (using if_bridge(4) and vtnet(4) with mtu 9000) Message-ID: <585BB81F.2020001@omnilan.de> In-Reply-To: <9b7951c0-9466-2b89-84de-c1026ee8f1c0@yandex.ru> References: <585AA902.50907@omnilan.de> <9b7951c0-9466-2b89-84de-c1026ee8f1c0@yandex.ru>
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Bezüglich Andrey V. Elsukov's Nachricht vom 22.12.2016 11:13 (localtime): > On 21.12.2016 19:08, Harry Schmalzbauer wrote: >> Hello, >> >> I'm having guest connectivity problems with jumbo frames. >> >> Since if_bridge(4) requires all interfaces to have the same MTU (and the >> uplink interface also handles iscsi traffic, which greatly benefits from >> jumbo frames), I >> 'ifconfig create vmnet0 mtu 9000' >> >> Now my problem is that I can't simply keep guest's mtu at 1500, since >> the host will send jumbo frames as answer wich never get through >> virtio-net. >> >> Does anybody have an idea how to fix/work arround? > > This looks like the problem with mbufs bigger than PAGE_SIZE. > Do you see some denied requests in the `netstat -m` output? Thanks for your attention! Nope, there are no denied mbuf requests after sending icmp echo-request through virtio-net with all participants' MTU set to 9000: 0/0/0 requests for mbufs denied (mbufs/clusters/mbuf+clusters) 0/0/0 requests for jumbo clusters denied (4k/9k/16k) 0 requests for sfbufs denied The icmp echo-reply just doesn't make it through virtio-net (the echo-request reaches the destination host, and the echo-reply reaches vmnet0!). Keeping everything untouched, just replacing '-s 5,virtio-net,vmnet0' with '-s 5,e1000,vmnet0', I get the reply into the guest: ping -D -s 8972 mirashare PING mirashare.egn.mo1.omnilan.net (172.21.34.11): 8972 data bytes 8980 bytes from 172.21.34.11: icmp_seq=0 ttl=64 time=1.590 ms Thanks, -harry
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