Two processes can bind to the same port

[Liam Young]

On both xenial and zesty apache and haproxy seem to be able to bind to the same port:

# netstat -peanut | grep 8776
tcp 0 0 0.0.0.0:8776 0.0.0.0:* LISTEN 0 76856 26190/haproxy
tcp6 0 0 :::8776 :::* LISTEN 0 76749 26254/apache2
tcp6 0 0 :::8776 :::* LISTEN 0 76857 26190/haproxy

I thought this should not be possible?

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-96-generic 4.4.0-96.119
ProcVersionSignature: Ubuntu 4.4.0-96.119-generic 4.4.83
Uname: Linux 4.4.0-96-generic x86_64
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Sep 29 11:46 seq
 crw-rw---- 1 root audio 116, 33 Sep 29 11:46 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CRDA: N/A
Date: Fri Sep 29 14:15:26 2017
Ec2AMI: ami-00000193
Ec2AMIManifest: FIXME
Ec2AvailabilityZone: nova
Ec2InstanceType: m1.blue
Ec2Kernel: unavailable
Ec2Ramdisk: unavailable
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lsusb:
 Bus 001 Device 002: ID 0627:0001 Adomax Technology Co., Ltd
 Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: OpenStack Foundation OpenStack Nova
PciMultimedia:

ProcEnviron:
 TERM=screen
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcFB:

ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-96-generic root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-96-generic N/A
 linux-backports-modules-4.4.0-96-generic N/A
 linux-firmware N/A
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: 1.10.1-1ubuntu1~cloud0
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-i440fx-zesty
dmi.modalias: dmi:bvnSeaBIOS:bvr1.10.1-1ubuntu1~cloud0:bd04/01/2014:svnOpenStackFoundation:pnOpenStackNova:pvr15.0.2:cvnQEMU:ct1:cvrpc-i440fx-zesty:
dmi.product.name: OpenStack Nova
dmi.product.version: 15.0.2
dmi.sys.vendor: OpenStack Foundation

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.14 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.14-rc2/

[Liam Young (gnuoy)]

Thanks for the suggestions. I will try with an upstream kernel and also add steps for reproducing

[Joseph Salisbury (jsalisbury)]

Thanks. I can try to reproduce this issue if you list the steps.

[Liam Young (gnuoy)]

Thanks jsalisbury. Ill try on another kernel now.

The steps to reproduce on xenial:

sudo su -
apt install --yes apache2 haproxy
echo "

listen test
    bind *:8776
    bind :::8776

" > /etc/haproxy/haproxy.cfg

echo "
Listen 8776
<VirtualHost *:8776>
        DocumentRoot /var/www/html
</VirtualHost>
" > /etc/apache2/sites-enabled/01-test.conf

systemctl restart haproxy
systemctl restart apache2
netstat -peanut | grep 8776

[Liam Young (gnuoy)]

I've retested with linux-image-4.4.9-040409-generic_4.4.9-040409.201605041832_amd64.deb but the image seems to persist.

[Liam Young (gnuoy)]

kernel-bug-exists-upstream

[Joseph Salisbury (jsalisbury)]

This issue appears to be an upstream bug, since you tested the latest upstream kernel. Would it be possible for you to open an upstream bug report[0]? That will allow the upstream Developers to examine the issue, and may provide a quicker resolution to the bug.

Please follow the instructions on the wiki page[0]. The first step is to email the appropriate mailing list. If no response is received, then a bug may be opened on bugzilla.kernel.org.

Once this bug is reported upstream, please add the tag: 'kernel-bug-reported-upstream'.

[0] https://wiki.ubuntu.com/Bugs/Upstream/kernel