[Bug 1791108] Re: open-iscsi uses domainsearch instead of search for /etc/resolv.conf

Wed Oct 3 16:14:54 UTC 2018

#VERIFICATION-BIONIC

- Before the update
ubuntu at iscsi-bionic:~$ dpkg -l | grep open-iscsi
ii  open-iscsi                            2.0.874-5ubuntu2.2                amd64        iSCSI initiator tools

ubuntu at iscsi-bionic:~$ cat /etc/resolv.conf 
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 192.168.122.1
domainsearch example.com

ubuntu at iscsi-bionic:~$ sudo strace ping -c1 www 2>&1 | grep www
execve("/bin/ping", ["ping", "-c1", "www"], 0x7ffeb4aecd70 /* 14 vars */) = 0
sendmmsg(5, [{msg_hdr={msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\300\17\1\0\0\1\0\0\0\0\0\0\3www\0\0\1\0\1", iov_len=21}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_TRUNC|MSG_DONTWAIT|MSG_EOR|MSG_WAITALL|MSG_CONFIRM|MSG_RST|MSG_MORE|MSG_BATCH|MSG_ZEROCOPY|MSG_FASTOPEN|0xb420000}, msg_len=21}, {msg_hdr={msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\0\31\1\0\0\1\0\0\0\0\0\0\3www\0\0\34\0\1", iov_len=21}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CTRUNC|MSG_FIN|MSG_SYN|MSG_CONFIRM|MSG_RST|MSG_MORE|MSG_BATCH|MSG_ZEROCOPY|MSG_FASTOPEN|0xb420010}, msg_len=21}], 2, MSG_NOSIGNAL) = 2 
recvfrom(5, "\300\17\201\203\0\1\0\0\0\0\0\0\3www\0\0\1\0\1", 2048, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("192.168.122.1")}, [28->16]) = 21
recvfrom(5, "\0\31\201\203\0\1\0\0\0\1\0\0\3www\0\0\34\0\1\0\0\6\0\1\0\0\"L\0@"..., 65536, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("192.168.122.1")}, [28->16]) = 96
write(2, "ping: www: Name or service not k"..., 37ping: www: Name or service not known

- After the update
ubuntu at iscsi-bionic:~$ dpkg -l | grep open-iscsi
ii  open-iscsi                            2.0.874-5ubuntu2.3                amd64        iSCSI initiator tools

ubuntu at iscsi-bionic:~$ cat /etc/resolv.conf 
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 192.168.122.1
search example.com

ubuntu at iscsi-bionic:~$ sudo strace ping -c1 www 2>&1 | grep www
execve("/bin/ping", ["ping", "-c1", "www"], 0x7ffea5cd0390 /* 14 vars */) = 0
sendmmsg(5, [{msg_hdr={msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\262\224\1\0\0\1\0\0\0\0\0\0\3www\7example\3com\0\0\1\0"..., iov_len=33}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_TRUNC|MSG_DONTWAIT|MSG_EOR|MSG_WAITALL|MSG_CONFIRM|MSG_ERRQUEUE|MSG_NOSIGNAL|MSG_MORE|MSG_BATCH|MSG_ZEROCOPY|MSG_CMSG_CLOEXEC|0x1b480000}, msg_len=33}, {msg_hdr={msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\226\235\1\0\0\1\0\0\0\0\0\0\3www\7example\3com\0\0\34\0"..., iov_len=33}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CTRUNC|MSG_FIN|MSG_SYN|MSG_CONFIRM|MSG_ERRQUEUE|MSG_NOSIGNAL|MSG_MORE|MSG_BATCH|MSG_ZEROCOPY|MSG_CMSG_CLOEXEC|0x1b480010}, msg_len=33}], 2, MSG_NOSIGNAL) = 2
recvfrom(5, "\262\224\201\200\0\1\0\1\0\0\0\0\3www\7example\3com\0\0\1\0"..., 2048, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("192.168.122.1")}, [28->16]) = 49
recvfrom(5, "\226\235\201\200\0\1\0\1\0\2\0\4\3www\7example\3com\0\0\34\0"..., 65536, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("192.168.122.1")}, [28->16]) = 197
write(1, "PING www.example.com (93.184.216"..., 132PING www.example.com (93.184.216.34) 56(84) bytes of data.
write(1, "--- www.example.com ping statist"..., 114--- www.example.com ping statistics ---

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https://bugs.launchpad.net/bugs/1791108

Title:
  open-iscsi uses domainsearch instead of search for /etc/resolv.conf

Status in open-iscsi package in Ubuntu:
  Fix Released
Status in open-iscsi source package in Xenial:
  Fix Committed
Status in open-iscsi source package in Bionic:
  Fix Committed
Status in open-iscsi source package in Cosmic:
  Fix Released

Bug description:
  [Impact]

  * open-iscsi is adding "domainsearch", a non-existent configuration
  option, instead of "search" in /etc/resolv.conf. As a result, the
  search list is ignored in the clients.

  [Test case]

  * Install an ubuntu machine that uses iscsi as root, and does not use systemd-resolvd.
  * Prepare the dhcp server to provide the search list to its clients. For instance, in dnsmasq:

  dhcp-option=option:domain-search,canonical.com

  * Boot the machine and check the content of /etc/resolv.conf
  - if domainsearch is present, the search list will be ignored:

  root at iscsi-xenial:/home/ubuntu# ping -c1 golem
  ping: unknown host golem

  root at iscsi-xenial:/home/ubuntu# strace ping -c1 golem 2>&1 | grep golem
  execve("/bin/ping", ["ping", "-c1", "golem"], [/* 19 vars */]) = 0
  sendto(4, "_(\1\0\0\1\0\0\0\0\0\0\5golem\0\0\1\0\1", 23, MSG_NOSIGNAL, NULL, 0) = 23
  recvfrom(4, "_(\201\203\0\1\0\0\0\0\0\0\5golem\0\0\1\0\1", 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("192.168.122.1")}, [16]) = 23
  write(2, "ping: unknown host golem\n", 25ping: unknown host golem

  - if search is present, the search list will be used:

  root at iscsi-xenial:/home/ubuntu# ping -c1 golem
  PING golem.canonical.com (91.189.89.199) 56(84) bytes of data.
  64 bytes from golem.canonical.com (91.189.89.199): icmp_seq=1 ttl=57 time=63.7 ms

  --- golem.canonical.com ping statistics ---
  1 packets transmitted, 1 received, 0% packet loss, time 0ms
  rtt min/avg/max/mdev = 63.735/63.735/63.735/0.000 ms

  root at iscsi-xenial:/home/ubuntu# strace ping -c1 golem 2>&1 | grep golem
  execve("/bin/ping", ["ping", "-c1", "golem"], [/* 19 vars */]) = 0
  sendto(4, "\1\\\1\0\0\1\0\0\0\0\0\0\5golem\tcanonical\3com"..., 37, MSG_NOSIGNAL, NULL, 0) = 37
  recvfrom(4, "\1\\\201\200\0\1\0\1\0\0\0\0\5golem\tcanonical\3com"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("192.168.122.1")}, [16]) = 53
  write(1, "PING golem.canonical.com (91.189"..., 145PING golem.canonical.com (91.189.89.199) 56(84) bytes of data.
  64 bytes from golem.canonical.com (91.189.89.199): icmp_seq=1 ttl=57 time=63.5 ms
  write(1, "--- golem.canonical.com ping sta"..., 157--- golem.canonical.com ping statistics ---

  [Regression potential]

  * The change is minor (a string replacement) and it's currently not working.
  * Any possible regression would involve continuing to break DNS resolution.

  [Other info]

  * resolv.conf man page: http://man7.org/linux/man-
  pages/man5/resolv.conf.5.html

  [Original description]

  Having an interface file such as /run/net-eno2.conf with the following
  content:

  DEVICE='eno2'
  PROTO='dhcp'
  IPV4ADDR='10.10.10.10'
  IPV4BROADCAST='10.10.10.255'
  IPV4NETMASK='255.255.255.0'
  IPV4GATEWAY='10.10.10.1'
  IPV4DNS0='169.254.169.254'
  IPV4DNS1='0.0.0.0'
  HOSTNAME=''
  DNSDOMAIN='test.com'
  NISDOMAIN=''
  ROOTSERVER='169.254.169.254'
  ROOTPATH=''
  filename='/ipxe.efi'
  UPTIME='45'
  DHCPLEASETIME='86400'
  DOMAINSEARCH='test.com'

  net-interface-handler translates it to:

  nameserver 169.254.169.254
  domainsearch test.com

  instead of:

  nameserver 169.254.169.254
  search test.com

  The problem is that domainsearch is not a valid configuration option
  for /etc/resolv.conf and is ignored.

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