Public bug reported: It happened in one of our production instances. Suddenly fails to resolve the hostname. Later I found it has happened if the DNS response message is bigger than 512 bytes. But never reproduced from other instances which have the same instance template.
with nslookup ```bash $ nslookup pod51041.outlook.com ;; Truncated, retrying in TCP mode. ;; Connection to 127.0.0.53#53(127.0.0.53) for pod51041.outlook.com failed: timed out. ``` and dig with another address. ```bash $ time dig +noanswer +noedns toomany.ddstreet.org ;; Truncated, retrying in TCP mode. ;; Connection to 127.0.0.53#53(127.0.0.53) for toomany.ddstreet.org failed: timed out. real 0m7.070s user 0m0.004s sys 0m0.004s ``` system versions ```bash $ systemctl --version systemd 245 (245.4-4ubuntu3.15) +PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid $ cat /etc/os-release NAME="Ubuntu" VERSION="20.04.2 LTS (Focal Fossa)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 20.04.2 LTS" VERSION_ID="20.04" HOME_URL="https://www.ubuntu.com/"; SUPPORT_URL="https://help.ubuntu.com/"; BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"; PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"; VERSION_CODENAME=focal UBUNTU_CODENAME=focal $ uname -r 5.8.0-1041-aws ``` status ```bash $ resolvectl status Global LLMNR setting: no MulticastDNS setting: no DNSOverTLS setting: no DNSSEC setting: no DNSSEC supported: no DNSSEC NTA: 10.in-addr.arpa 16.172.in-addr.arpa 168.192.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa corp d.f.ip6.arpa home internal intranet lan local private test Link 2 (ens5) Current Scopes: DNS DefaultRoute setting: yes LLMNR setting: yes MulticastDNS setting: no DNSOverTLS setting: no DNSSEC setting: no DNSSEC supported: no Current DNS Server: 172.29.0.2 DNS Servers: 172.29.0.2 DNS Domain: ap-south-1.compute.internal ``` strace to resolved process ```bash $ strace -fp $(which systemd-resolved) epoll_pwait(4, [{EPOLLIN, {u32=3491475680, u64=187650612637920}}], 14, -1, NULL, 8) = 1 recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 38 recvmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(52259), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=128->16, msg_iov=[{iov_base="\344g\1 \0\1\0\0\0\0\0\0\10pod51041\7outlook\3com\0\0\1\0\1", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={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, cmsg_data=[64]}], msg_controllen=56, msg_flags=0}, 0) = 38 newfstatat(AT_FDCWD, "/etc/hosts", {st_mode=S_IFREG|0644, st_size=262, ...}, 0) = 0 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 getrandom("\x62\xe8", 2, GRND_NONBLOCK) = 2 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 sendmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(52259), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=16, msg_iov=[{iov_base="\344g\203\200\0\1\0\35\0\0\0\0\10pod51041\7outlook\3com\0\0\1\0\1\300\f\0\1\0\1\0\0\0\36\0\0044`zB\300\f\0\1\0\1\0\0\0\36\0\0044`\243\"\300\f\0\1\0\1\0\0\0\36\0\0044`+\242\300\f\0\1\0\1\0\0\0\36\0\4(a\226\362\300\f\0\1\0\1\0\0\0\36\0\0044`%\"\300\f\0\1\0\1\0\0\0\36\0\0044`Ob\300\f\0\1\0\1\0\0\0\36\0\0044`y\242\300\f\0\1\0\1\0\0\0\36\0\0044`y\362\300\f\0\1\0\1\0\0\0\36\0\0044`\2432\300\f\0\1\0\1\0\0\0\36\0\0044`q\202\300\f\0\1\0\1\0\0\0\36\0\0044`y\222\300\f\0\1\0\1\0\0\0\36\0\0044`z\22\300\f\0\1\0\1\0\0\0\36\0\0044`y\342\300\f\0\1\0\1\0\0\0\36\0\0044`wb\300\f\0\1\0\1\0\0\0\36\0\0044`yb\300\f\0\1\0\1\0\0\0\36\0\0044`y\"\300\f\0\1\0\1\0\0\0\36\0\0044`y\22\300\f\0\1\0\1\0\0\0\36\0\0044`q\322\300\f\0\1\0\1\0\0\0\36\0\0044`q\342\300\f\0\1\0\1\0\0\0\36\0\0044`q\222\300\f\0\1\0\1\0\0\0\36\0\0044`y2\300\f\0\1\0\1\0\0\0\36\0\0044`y\2\300\f\0\1\0\1\0\0\0\36\0\0044`q\262\300\f\0\1\0\1\0\0\0\36\0\0044`z2\300\f\0\1\0\1\0\0\0\36\0\0044`wR\300\f\0\1\0\1\0\0\0\36\0\0044`y\202\300\f\0\1\0\1\0\0\0\36\0\0044`z\"\300\f\0\1\0\1\0\0\0\36\0\0044`q\302\300\f\0\1\0\1\0\0\0\36\0\0044`\3\262", iov_len=502}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("0.0.0.0")}}], msg_controllen=28, msg_flags=0}, 0) = 502 gettid() = 607 epoll_pwait(4, [{EPOLLIN, {u32=3491475680, u64=187650612637920}}], 14, -1, NULL, 8) = 1 recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 53 recvmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(37976), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=128->16, msg_iov=[{iov_base="\335H\1\0\0\1\0\0\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={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, cmsg_data=[64]}], msg_controllen=56, msg_flags=0}, 0) = 53 newfstatat(AT_FDCWD, "/etc/hosts", {st_mode=S_IFREG|0644, st_size=262, ...}, 0) = 0 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 getrandom("\xaf\x1e", 2, GRND_NONBLOCK) = 2 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 15 setsockopt(15, SOL_IP, IP_UNICAST_IF, [33554432], 4) = 0 setsockopt(15, SOL_IP, IP_RECVERR, [1], 4) = 0 setsockopt(15, SOL_IP, IP_PKTINFO, [1], 4) = 0 connect(15, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, 16) = 0 epoll_ctl(4, EPOLL_CTL_ADD, 15, {EPOLLIN, {u32=3491583952, u64=187650612746192}}) = 0 write(15, "\257\36\1\0\0\1\0\0\0\0\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1\0\0)\2\0\0\0\0\0\0\0", 64) = 64 gettid() = 607 timerfd_settime(11, TFD_TIMER_ABSTIME, {it_interval={tv_sec=0, tv_nsec=0}, it_value={tv_sec=105529, tv_nsec=683183000}}, NULL) = 0 epoll_pwait(4, [{EPOLLIN, {u32=3491475680, u64=187650612637920}}], 17, -1, NULL, 8) = 1 recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 53 recvmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(54540), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=128->16, msg_iov=[{iov_base="\2504\1\0\0\1\0\0\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={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, cmsg_data=[64]}], msg_controllen=56, msg_flags=0}, 0) = 53 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 getrandom("\xc8\xc3", 2, GRND_NONBLOCK) = 2 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 16 setsockopt(16, SOL_IP, IP_UNICAST_IF, [33554432], 4) = 0 setsockopt(16, SOL_IP, IP_RECVERR, [1], 4) = 0 setsockopt(16, SOL_IP, IP_PKTINFO, [1], 4) = 0 connect(16, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, 16) = 0 epoll_ctl(4, EPOLL_CTL_ADD, 16, {EPOLLIN, {u32=3491849328, u64=187650613011568}}) = 0 write(16, "\310\303\1\0\0\1\0\0\0\0\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1\0\0)\2\0\0\0\0\0\0\0", 64) = 64 gettid() = 607 epoll_pwait(4, [{EPOLLIN, {u32=3491583952, u64=187650612746192}}], 20, -1, NULL, 8) = 1 recvfrom(15, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 146 recvmsg(15, {msg_name={sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, msg_namelen=128->16, msg_iov=[{iov_base="\257\36\201\200\0\1\0\0\0\1\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1\300\f\0\6\0\1\0\0\0\1\0F\7ns-1164\tawsdns-17\3org\0\21awsdns-hostmaster\6amazon\300,\0\0\0\1\0\0\34 \0\0\3\204\0\22u\0\0\0\0<\0\0)\20\0\0\0\0\0\0\0", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("ens5"), ipi_spec_dst=inet_addr("172.29.40.107"), ipi_addr=inet_addr("172.29.40.107")}}], msg_controllen=32, msg_flags=0}, 0) = 146 epoll_ctl(4, EPOLL_CTL_DEL, 15, NULL) = 0 close(15) = 0 sendmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(37976), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=16, msg_iov=[{iov_base="\335H\201\200\0\1\0\0\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1", iov_len=53}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("0.0.0.0")}}], msg_controllen=28, msg_flags=0}, 0) = 53 gettid() = 607 epoll_pwait(4, [{EPOLLIN, {u32=3491849328, u64=187650613011568}}], 17, -1, NULL, 8) = 1 recvfrom(16, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 80 recvmsg(16, {msg_name={sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, msg_namelen=128->16, msg_iov=[{iov_base="\310\303\201\200\0\1\0\1\0\0\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1\300\f\0\1\0\1\0\0\0\27\0\0044_P\272\0\0)\20\0\0\0\0\0\0\0", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("ens5"), ipi_spec_dst=inet_addr("172.29.40.107"), ipi_addr=inet_addr("172.29.40.107")}}], msg_controllen=32, msg_flags=0}, 0) = 80 epoll_ctl(4, EPOLL_CTL_DEL, 16, NULL) = 0 close(16) = 0 sendmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(54540), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=16, msg_iov=[{iov_base="\2504\201\200\0\1\0\1\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1\300\f\0\1\0\1\0\0\0\27\0\0044_P\272", iov_len=69}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("0.0.0.0")}}], msg_controllen=28, msg_flags=0}, 0) = 69 gettid() = 607 timerfd_settime(11, TFD_TIMER_ABSTIME, {it_interval={tv_sec=0, tv_nsec=0}, it_value={tv_sec=0, tv_nsec=0}}, NULL) = 0 epoll_pwait(4, ^Cstrace: Process 607 detached ``` In a normal case, I can see that the systemd-resolved creates a UDP socket first and a TCP socket later. But in this case, it never creates a TCP socket and just retries with UDP again while the client sent TCP packets. ** Affects: systemd (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1966775 Title: systemd-resolved fails resolution via TCP Status in systemd package in Ubuntu: New Bug description: It happened in one of our production instances. Suddenly fails to resolve the hostname. Later I found it has happened if the DNS response message is bigger than 512 bytes. But never reproduced from other instances which have the same instance template. with nslookup ```bash $ nslookup pod51041.outlook.com ;; Truncated, retrying in TCP mode. ;; Connection to 127.0.0.53#53(127.0.0.53) for pod51041.outlook.com failed: timed out. ``` and dig with another address. ```bash $ time dig +noanswer +noedns toomany.ddstreet.org ;; Truncated, retrying in TCP mode. ;; Connection to 127.0.0.53#53(127.0.0.53) for toomany.ddstreet.org failed: timed out. real 0m7.070s user 0m0.004s sys 0m0.004s ``` system versions ```bash $ systemctl --version systemd 245 (245.4-4ubuntu3.15) +PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid $ cat /etc/os-release NAME="Ubuntu" VERSION="20.04.2 LTS (Focal Fossa)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 20.04.2 LTS" VERSION_ID="20.04" HOME_URL="https://www.ubuntu.com/"; SUPPORT_URL="https://help.ubuntu.com/"; BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"; PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"; VERSION_CODENAME=focal UBUNTU_CODENAME=focal $ uname -r 5.8.0-1041-aws ``` status ```bash $ resolvectl status Global LLMNR setting: no MulticastDNS setting: no DNSOverTLS setting: no DNSSEC setting: no DNSSEC supported: no DNSSEC NTA: 10.in-addr.arpa 16.172.in-addr.arpa 168.192.in-addr.arpa 17.172.in-addr.arpa 18.172.in-addr.arpa 19.172.in-addr.arpa 20.172.in-addr.arpa 21.172.in-addr.arpa 22.172.in-addr.arpa 23.172.in-addr.arpa 24.172.in-addr.arpa 25.172.in-addr.arpa 26.172.in-addr.arpa 27.172.in-addr.arpa 28.172.in-addr.arpa 29.172.in-addr.arpa 30.172.in-addr.arpa 31.172.in-addr.arpa corp d.f.ip6.arpa home internal intranet lan local private test Link 2 (ens5) Current Scopes: DNS DefaultRoute setting: yes LLMNR setting: yes MulticastDNS setting: no DNSOverTLS setting: no DNSSEC setting: no DNSSEC supported: no Current DNS Server: 172.29.0.2 DNS Servers: 172.29.0.2 DNS Domain: ap-south-1.compute.internal ``` strace to resolved process ```bash $ strace -fp $(which systemd-resolved) epoll_pwait(4, [{EPOLLIN, {u32=3491475680, u64=187650612637920}}], 14, -1, NULL, 8) = 1 recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 38 recvmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(52259), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=128->16, msg_iov=[{iov_base="\344g\1 \0\1\0\0\0\0\0\0\10pod51041\7outlook\3com\0\0\1\0\1", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={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, cmsg_data=[64]}], msg_controllen=56, msg_flags=0}, 0) = 38 newfstatat(AT_FDCWD, "/etc/hosts", {st_mode=S_IFREG|0644, st_size=262, ...}, 0) = 0 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 getrandom("\x62\xe8", 2, GRND_NONBLOCK) = 2 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 sendmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(52259), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=16, msg_iov=[{iov_base="\344g\203\200\0\1\0\35\0\0\0\0\10pod51041\7outlook\3com\0\0\1\0\1\300\f\0\1\0\1\0\0\0\36\0\0044`zB\300\f\0\1\0\1\0\0\0\36\0\0044`\243\"\300\f\0\1\0\1\0\0\0\36\0\0044`+\242\300\f\0\1\0\1\0\0\0\36\0\4(a\226\362\300\f\0\1\0\1\0\0\0\36\0\0044`%\"\300\f\0\1\0\1\0\0\0\36\0\0044`Ob\300\f\0\1\0\1\0\0\0\36\0\0044`y\242\300\f\0\1\0\1\0\0\0\36\0\0044`y\362\300\f\0\1\0\1\0\0\0\36\0\0044`\2432\300\f\0\1\0\1\0\0\0\36\0\0044`q\202\300\f\0\1\0\1\0\0\0\36\0\0044`y\222\300\f\0\1\0\1\0\0\0\36\0\0044`z\22\300\f\0\1\0\1\0\0\0\36\0\0044`y\342\300\f\0\1\0\1\0\0\0\36\0\0044`wb\300\f\0\1\0\1\0\0\0\36\0\0044`yb\300\f\0\1\0\1\0\0\0\36\0\0044`y\"\300\f\0\1\0\1\0\0\0\36\0\0044`y\22\300\f\0\1\0\1\0\0\0\36\0\0044`q\322\300\f\0\1\0\1\0\0\0\36\0\0044`q\342\300\f\0\1\0\1\0\0\0\36\0\0044`q\222\300\f\0\1\0\1\0\0\0\36\0\0044`y2\300\f\0\1\0\1\0\0\0\36\0\0044`y\2\300\f\0\1\0\1\0\0\0\36\0\0044`q\262\300\f\0\1\0\1\0\0\0\36\0\0044`z2\300\f\0\1\0\1\0\0\0\36\0\0044`wR\300\f\0\1\0\1\0\0\0\36\0\0044`y\202\300\f\0\1\0\1\0\0\0\36\0\0044`z\"\300\f\0\1\0\1\0\0\0\36\0\0044`q\302\300\f\0\1\0\1\0\0\0\36\0\0044`\3\262", iov_len=502}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("0.0.0.0")}}], msg_controllen=28, msg_flags=0}, 0) = 502 gettid() = 607 epoll_pwait(4, [{EPOLLIN, {u32=3491475680, u64=187650612637920}}], 14, -1, NULL, 8) = 1 recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 53 recvmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(37976), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=128->16, msg_iov=[{iov_base="\335H\1\0\0\1\0\0\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={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, cmsg_data=[64]}], msg_controllen=56, msg_flags=0}, 0) = 53 newfstatat(AT_FDCWD, "/etc/hosts", {st_mode=S_IFREG|0644, st_size=262, ...}, 0) = 0 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 getrandom("\xaf\x1e", 2, GRND_NONBLOCK) = 2 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 15 setsockopt(15, SOL_IP, IP_UNICAST_IF, [33554432], 4) = 0 setsockopt(15, SOL_IP, IP_RECVERR, [1], 4) = 0 setsockopt(15, SOL_IP, IP_PKTINFO, [1], 4) = 0 connect(15, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, 16) = 0 epoll_ctl(4, EPOLL_CTL_ADD, 15, {EPOLLIN, {u32=3491583952, u64=187650612746192}}) = 0 write(15, "\257\36\1\0\0\1\0\0\0\0\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1\0\0)\2\0\0\0\0\0\0\0", 64) = 64 gettid() = 607 timerfd_settime(11, TFD_TIMER_ABSTIME, {it_interval={tv_sec=0, tv_nsec=0}, it_value={tv_sec=105529, tv_nsec=683183000}}, NULL) = 0 epoll_pwait(4, [{EPOLLIN, {u32=3491475680, u64=187650612637920}}], 17, -1, NULL, 8) = 1 recvfrom(12, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 53 recvmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(54540), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=128->16, msg_iov=[{iov_base="\2504\1\0\0\1\0\0\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={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, cmsg_data=[64]}], msg_controllen=56, msg_flags=0}, 0) = 53 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 getrandom("\xc8\xc3", 2, GRND_NONBLOCK) = 2 newfstatat(AT_FDCWD, "/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/resolv.conf", {st_mode=S_IFREG|0644, st_size=622, ...}, 0) = 0 newfstatat(AT_FDCWD, "/run/systemd/resolve/stub-resolv.conf", {st_mode=S_IFREG|0644, st_size=752, ...}, 0) = 0 socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 16 setsockopt(16, SOL_IP, IP_UNICAST_IF, [33554432], 4) = 0 setsockopt(16, SOL_IP, IP_RECVERR, [1], 4) = 0 setsockopt(16, SOL_IP, IP_PKTINFO, [1], 4) = 0 connect(16, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, 16) = 0 epoll_ctl(4, EPOLL_CTL_ADD, 16, {EPOLLIN, {u32=3491849328, u64=187650613011568}}) = 0 write(16, "\310\303\1\0\0\1\0\0\0\0\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1\0\0)\2\0\0\0\0\0\0\0", 64) = 64 gettid() = 607 epoll_pwait(4, [{EPOLLIN, {u32=3491583952, u64=187650612746192}}], 20, -1, NULL, 8) = 1 recvfrom(15, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 146 recvmsg(15, {msg_name={sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, msg_namelen=128->16, msg_iov=[{iov_base="\257\36\201\200\0\1\0\0\0\1\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1\300\f\0\6\0\1\0\0\0\1\0F\7ns-1164\tawsdns-17\3org\0\21awsdns-hostmaster\6amazon\300,\0\0\0\1\0\0\34 \0\0\3\204\0\22u\0\0\0\0<\0\0)\20\0\0\0\0\0\0\0", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("ens5"), ipi_spec_dst=inet_addr("172.29.40.107"), ipi_addr=inet_addr("172.29.40.107")}}], msg_controllen=32, msg_flags=0}, 0) = 146 epoll_ctl(4, EPOLL_CTL_DEL, 15, NULL) = 0 close(15) = 0 sendmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(37976), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=16, msg_iov=[{iov_base="\335H\201\200\0\1\0\0\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\34\0\1", iov_len=53}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("0.0.0.0")}}], msg_controllen=28, msg_flags=0}, 0) = 53 gettid() = 607 epoll_pwait(4, [{EPOLLIN, {u32=3491849328, u64=187650613011568}}], 17, -1, NULL, 8) = 1 recvfrom(16, NULL, 0, MSG_PEEK|MSG_TRUNC, NULL, NULL) = 80 recvmsg(16, {msg_name={sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("172.29.0.2")}, msg_namelen=128->16, msg_iov=[{iov_base="\310\303\201\200\0\1\0\1\0\0\0\1\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1\300\f\0\1\0\1\0\0\0\27\0\0044_P\272\0\0)\20\0\0\0\0\0\0\0", iov_len=3928}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("ens5"), ipi_spec_dst=inet_addr("172.29.40.107"), ipi_addr=inet_addr("172.29.40.107")}}], msg_controllen=32, msg_flags=0}, 0) = 80 epoll_ctl(4, EPOLL_CTL_DEL, 16, NULL) = 0 close(16) = 0 sendmsg(12, {msg_name={sa_family=AF_INET, sin_port=htons(54540), sin_addr=inet_addr("127.0.0.1")}, msg_namelen=16, msg_iov=[{iov_base="\2504\201\200\0\1\0\1\0\0\0\0\nmonitoring\nap-south-1\tamazonaws\3com\0\0\1\0\1\300\f\0\1\0\1\0\0\0\27\0\0044_P\272", iov_len=69}], msg_iovlen=1, msg_control=[{cmsg_len=28, cmsg_level=SOL_IP, cmsg_type=IP_PKTINFO, cmsg_data={ipi_ifindex=if_nametoindex("lo"), ipi_spec_dst=inet_addr("127.0.0.53"), ipi_addr=inet_addr("0.0.0.0")}}], msg_controllen=28, msg_flags=0}, 0) = 69 gettid() = 607 timerfd_settime(11, TFD_TIMER_ABSTIME, {it_interval={tv_sec=0, tv_nsec=0}, it_value={tv_sec=0, tv_nsec=0}}, NULL) = 0 epoll_pwait(4, ^Cstrace: Process 607 detached ``` In a normal case, I can see that the systemd-resolved creates a UDP socket first and a TCP socket later. But in this case, it never creates a TCP socket and just retries with UDP again while the client sent TCP packets. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1966775/+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
