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Date:      Fri, 18 Aug 2023 14:54:01 -0700
From:      Kevin Oberman <rkoberman@gmail.com>
To:        =?UTF-8?B?Sm9zw6kgUMOpcmV6?= <fbl@aoek.com>
Cc:        freebsd-net@freebsd.org
Subject:   Re: em0: No buffer space available for IPv6 traffic but IPv4 is OK
Message-ID:  <CAN6yY1t80K6PibY_iOfsfyrbOE--yRyE0=DXX1Fpjk0pBJZ=fA@mail.gmail.com>
In-Reply-To: <503561ece3e7201318c298c2d5b91eb5@mail.yourbox.net>
References:  <503561ece3e7201318c298c2d5b91eb5@mail.yourbox.net>

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On Fri, Aug 18, 2023 at 1:02=E2=80=AFAM Jos=C3=A9 P=C3=A9rez <fbl@aoek.com>=
 wrote:

> Hi,
> on this intel em0
> # dmesg |fgrep em0
> em0: <Intel(R) Gigabit CT 82574L> port 0xd800-0xd81f mem
> 0xfe9e0000-0xfe9fffff,0xfe9dc000-0xfe9dffff irq 48 at device 0.0 on pci1
> em0: Using 1024 TX descriptors and 1024 RX descriptors
> em0: Using 2 RX queues 2 TX queues
> em0: Using MSI-X interrupts with 3 vectors
> em0: Ethernet address: xx:xx:xx:xx:xx:xx
> em0: netmap queues/slots: TX 2/1024, RX 2/1024
>
> IPv4 and IPv6 used to work seamlessly for the past 6+ years.
>
> # ifconfig em0
> em0: flags=3D8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu
> 1500
>
>
> options=3D81249b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,LRO,WO=
L_MAGIC,VLAN_HWFILTER>
>          ether xx:xx:xx:xx:xx:xx
>          inet xxx.xxx.xxx.xxx netmask 0xffffff00 broadcast
> xxx.xxx.xxx.255
>          inet6 fe80::xxxx:xxxx:xxxx:xxxx%em0 prefixlen 64 scopeid 0x1
>          inet6 2xxx:xxxx:xxxx:xxxx::1 prefixlen 64
>          media: Ethernet autoselect (100baseTX <full-duplex>)
>          status: active
>          nd6 options=3D23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>
>
> Nevertheless, now IPv6 traffic does not work anymore:
> # ping6 www.google.com
> PING6(56=3D40+8+8 bytes) 2xxx:xxxx:xxxx:xxxx::1 --> 2yyy:yyyy:yyyy:yyyy::=
1
> ping6: sendmsg: No buffer space available
> ping6: wrote www.google.com 16 chars, ret=3D-1
>
>  From send(2):
> [...]
>       [ENOBUFS]          The system was unable to allocate an internal
> buffer.
>                          The operation may succeed when buffers become
>                          available.
>
>       [ENOBUFS]          The output queue for a network interface was
> full.
>                          This generally indicates that the interface has
>                          stopped sending, but may be caused by transient
>                          congestion.
> [...]
>
> There is little traffic on the interface and it seems that buffers are
> available:
> # netstat -m
> 2108/3472/5580 mbufs in use (current/cache/total)
> 2062/1336/3398/1018874 mbuf clusters in use (current/cache/total/max)
> 15/1250 mbuf+clusters out of packet secondary zone in use
> (current/cache)
> [...]
>
> Interestingly, there is incoming IPv6 local broadcast traffic as sniffed
> by
> # tcpdump -n -i em0 ip6
> (ICMP6, neighbor solicitation, UDP from LAN link local addresses).
>
> Has anyone seen this before and can suggest a fix?
>
> Reboot did not solve, no software updates made, no config changes, just
> stop working from one day to the next.
>
> Thank you.
>
> --
> Jos=C3=A9 P=C3=A9rez
>

Oddly, ENOBUFS is the error I get when my firewall is blocking transmit
traffic. There may well be other causes.
--=20
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman@gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683

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<div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"gmail_default" style=3D"fon=
t-family:tahoma,sans-serif;font-size:small">On Fri, Aug 18, 2023 at 1:02=E2=
=80=AFAM Jos=C3=A9 P=C3=A9rez &lt;<a href=3D"mailto:fbl@aoek.com">fbl@aoek.=
com</a>&gt; wrote:</div></div><div class=3D"gmail_quote"><blockquote class=
=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rg=
b(204,204,204);padding-left:1ex">Hi,<br>
on this intel em0<br>
# dmesg |fgrep em0<br>
em0: &lt;Intel(R) Gigabit CT 82574L&gt; port 0xd800-0xd81f mem <br>
0xfe9e0000-0xfe9fffff,0xfe9dc000-0xfe9dffff irq 48 at device 0.0 on pci1<br=
>
em0: Using 1024 TX descriptors and 1024 RX descriptors<br>
em0: Using 2 RX queues 2 TX queues<br>
em0: Using MSI-X interrupts with 3 vectors<br>
em0: Ethernet address: xx:xx:xx:xx:xx:xx<br>
em0: netmap queues/slots: TX 2/1024, RX 2/1024<br>
<br>
IPv4 and IPv6 used to work seamlessly for the past 6+ years.<br>
<br>
# ifconfig em0<br>
em0: flags=3D8843&lt;UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST&gt; metric 0 mt=
u <br>
1500<br>
<br>
options=3D81249b&lt;RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,LRO,W=
OL_MAGIC,VLAN_HWFILTER&gt;<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0ether xx:xx:xx:xx:xx:xx<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0inet xxx.xxx.xxx.xxx netmask 0xffffff00 b=
roadcast <br>
xxx.xxx.xxx.255<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0inet6 fe80::xxxx:xxxx:xxxx:xxxx%em0 prefi=
xlen 64 scopeid 0x1<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0inet6 2xxx:xxxx:xxxx:xxxx::1 prefixlen 64=
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0media: Ethernet autoselect (100baseTX &lt=
;full-duplex&gt;)<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0status: active<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0nd6 options=3D23&lt;PERFORMNUD,ACCEPT_RTA=
DV,AUTO_LINKLOCAL&gt;<br>
<br>
Nevertheless, now IPv6 traffic does not work anymore:<br>
# ping6 <a href=3D"http://www.google.com" rel=3D"noreferrer" target=3D"_bla=
nk">www.google.com</a><br>
PING6(56=3D40+8+8 bytes) 2xxx:xxxx:xxxx:xxxx::1 --&gt; 2yyy:yyyy:yyyy:yyyy:=
:1<br>
ping6: sendmsg: No buffer space available<br>
ping6: wrote <a href=3D"http://www.google.com" rel=3D"noreferrer" target=3D=
"_blank">www.google.com</a> 16 chars, ret=3D-1<br>
<br>
=C2=A0From send(2):<br>
[...]<br>
=C2=A0 =C2=A0 =C2=A0 [ENOBUFS]=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 The system=
 was unable to allocate an internal <br>
buffer.<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0The operation may succeed when buffers become<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0available.<br>
<br>
=C2=A0 =C2=A0 =C2=A0 [ENOBUFS]=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 The output=
 queue for a network interface was <br>
full.<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0This generally indicates that the interface has<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0stopped sending, but may be caused by transient<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0congestion.<br>
[...]<br>
<br>
There is little traffic on the interface and it seems that buffers are <br>
available:<br>
# netstat -m<br>
2108/3472/5580 mbufs in use (current/cache/total)<br>
2062/1336/3398/1018874 mbuf clusters in use (current/cache/total/max)<br>
15/1250 mbuf+clusters out of packet secondary zone in use <br>
(current/cache)<br>
[...]<br>
<br>
Interestingly, there is incoming IPv6 local broadcast traffic as sniffed <b=
r>
by<br>
# tcpdump -n -i em0 ip6<br>
(ICMP6, neighbor solicitation, UDP from LAN link local addresses).<br>
<br>
Has anyone seen this before and can suggest a fix?<br>
<br>
Reboot did not solve, no software updates made, no config changes, just <br=
>
stop working from one day to the next.<br>
<br>
Thank you.<br>
<br>
-- <br>
Jos=C3=A9 P=C3=A9rez<br></blockquote><div><br></div><div style=3D"font-fami=
ly:tahoma,sans-serif;font-size:small" class=3D"gmail_default">Oddly, ENOBUF=
S is the error I get when my firewall is blocking transmit traffic. There m=
ay well be other causes.<br></div></div><span class=3D"gmail_signature_pref=
ix">-- </span><br><div dir=3D"ltr" class=3D"gmail_signature"><div dir=3D"lt=
r"><div><div dir=3D"ltr"><div><div dir=3D"ltr"><div><div dir=3D"ltr">Kevin =
Oberman, Part time kid herder and retired Network Engineer<br>E-mail: <a hr=
ef=3D"mailto:rkoberman@gmail.com" target=3D"_blank">rkoberman@gmail.com</a>=
<br></div><div>PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683</d=
iv></div></div></div></div></div></div></div></div>

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