I have this on Ubuntu 18.04. In my case I use dnsmasq with a custom configuration providing DHCP and DNS to multiple bridges (Virtual Machines and containers). So I need them both (in so far as I need dnsmasq and am being forced to use systemd).
The problem is a DNS loop between systemd and dnsmasq. systemd-resolved forwards DNS queries in parallel to entries in /etc/resolv.conf and servers picked up from interfaces via DHCP. If you, like me have dnsmasq in resolv.conf, and a dnsmasq configuration that forwards to systemd, then you have a loop. My work-around is to add `DNS=127.1.1.1` into /etc/systemd/resolved.conf. Nothing is listening on 127.1.1.1 so the queries go unanswered. The systemd resovler gets answers only from servers provided to me via DHCP or statically assigned to an interface. Inside my dnsmasq.conf I have `server=127.0.0.53`, and resolv.conf has `nameserver 127.0.0.1` which is dnsmasq. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to dnsmasq in Ubuntu. https://bugs.launchpad.net/bugs/1670959 Title: systemd-resolved using 100% CPU Status in dnsmasq package in Ubuntu: Confirmed Status in systemd package in Ubuntu: Confirmed Bug description: Sometimes systemd-resolved process is using 100% CPU. After a while it changes back to normal. It happens usually after connecting to the (wifi) network, like starting the OS. strace output: sendmsg(12, {msg_name(16)={sa_family=AF_INET, sin_port=htons(33589), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"6\215\201\200\0\1\0\1\0\0\0\1\4cs41\3wac\vedgecastcdn\3net\0\0\34\0\1\300\f\0\34\0\1\0\0\10\235\0\20&\6(\0\0024\0Y%L\4\6#f&\214\0\0)\377\326\0\0\0\0\0\0", 81}], msg_controllen=28, [{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, {ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("127.0.0.53")}}], msg_flags=0}, 0) = 81 sendmsg(3, {msg_name(0)=NULL, msg_iov(4)=[{"PRIORITY=6\nSYSLOG_FACILITY=3\nCODE_FILE=../src/resolve/resolved-dns-stub.c\nCODE_LINE=363\nCODE_FUNCTION=dns_stub_process_query\nSYSLOG_IDENTIFIER=systemd-resolved\n", 160}, {"MESSAGE=", 8}, {"Processing query...", 19}, {"\n", 1}], msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 188 epoll_wait(4, [{EPOLLIN, {u32=3176459184, u64=94565471415216}}], 16, -1) = 1 clock_gettime(CLOCK_BOOTTIME, {44665, 938069872}) = 0 recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 53 recvmsg(12, {msg_name(16)={sa_family=AF_INET, sin_port=htons(33589), sin_addr=inet_addr("127.0.0.1")}, msg_iov(1)=[{"Z\262\1\20\0\1\0\0\0\0\0\1\4cs41\3wac\vedgecastcdn\3net\0\0\34\0\1\0\0)\2\0\0\0\0\0\0\0", 3936}], msg_controllen=56, [{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, {ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("127.0.0.53")}}, {cmsg_len=20, cmsg_level=SOL_IP, cmsg_type=IP_TTL, {ttl=64}}], msg_flags=0}, 0) = 53 stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0 getrandom("\365I", 2, GRND_NONBLOCK) = 2 stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0 getrandom("\203;", 2, GRND_NONBLOCK) = 2 clock_gettime(CLOCK_BOOTTIME, {44665, 938446937}) = 0 open("/run/systemd/netif/links/3", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0 stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=303, ...}) = 0 socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 18 connect(18, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 16) = 0 epoll_ctl(4, EPOLL_CTL_ADD, 18, {EPOLLIN, {u32=3176610576, u64=94565471566608}}) = 0 write(18, "\203;\1\20\0\1\0\0\0\0\0\1\4cs41\3wac\vedgecastcdn\3net\0\0\34\0\1\0\0)\2\0\0\0\0\0\0\0", 53) = 53 clock_gettime(CLOCK_BOOTTIME, {44665, 938833717}) = 0 clock_gettime(CLOCK_BOOTTIME, {44665, 938875138}) = 0 epoll_ctl(4, EPOLL_CTL_DEL, 18, NULL) = 0 close(18) = 0 journalctl output: Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:35 parsec systemd-resolved[1512]: Processing query... Mar 08 08:25:41 parsec dnsmasq[1545]: Maximum number of concurrent DNS queries reached (max: 150) As you can see, I would use it together with dnsmasq. ProblemType: Bug DistroRelease: Ubuntu 17.04 Package: systemd 232-18ubuntu1 ProcVersionSignature: Ubuntu 4.10.0-9.11-generic 4.10.0 Uname: Linux 4.10.0-9-generic x86_64 NonfreeKernelModules: zfs zunicode zavl zcommon znvpair ApportVersion: 2.20.4-0ubuntu2 Architecture: amd64 Date: Wed Mar 8 08:20:18 2017 MachineType: Hewlett-Packard HP EliteBook Folio 1020 G1 ProcEnviron: LANGUAGE=en_US:en TERM=xterm PATH=(custom, no user) LANG=en_US.UTF-8 SHELL=/bin/zsh ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-4.10.0-9-generic root=UUID=a54fe703-35d4-47ac-9c6e-4034421531fb ro rootflags=subvol=@ SourcePackage: systemd UpgradeStatus: Upgraded to zesty on 2015-05-24 (653 days ago) dmi.bios.date: 03/09/2015 dmi.bios.vendor: Hewlett-Packard dmi.bios.version: M77 Ver. 01.05 dmi.board.name: 2271 dmi.board.vendor: Hewlett-Packard dmi.board.version: KBC Version 91.4C dmi.chassis.asset.tag: CNU51199KV dmi.chassis.type: 10 dmi.chassis.vendor: Hewlett-Packard dmi.modalias: dmi:bvnHewlett-Packard:bvrM77Ver.01.05:bd03/09/2015:svnHewlett-Packard:pnHPEliteBookFolio1020G1:pvrA3009DD18303:rvnHewlett-Packard:rn2271:rvrKBCVersion91.4C:cvnHewlett-Packard:ct10:cvr: dmi.product.name: HP EliteBook Folio 1020 G1 dmi.product.version: A3009DD18303 dmi.sys.vendor: Hewlett-Packard To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/dnsmasq/+bug/1670959/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
