bug#41234: 27.0.91; Synchronous network requests are failing with “Name or service not known”

[Dmitry Alexandrov]

FWIW, strace suggests, that the problematic Emacs process is trying to connect 
to an outdated nameserver (from a LAN this machine was connected once):

        …
        openat(AT_FDCWD, "/etc/hosts", O_RDONLY|O_CLOEXEC) = 12
        lseek(12, 0, SEEK_CUR)                  = 0
        fstat(12, {st_mode=S_IFREG|0644, st_size=184, ...}) = 0
        read(12, "127.0.0.1\tlocalhost\n127.0.1.1\tno"..., 4096) = 184
        lseek(12, 0, SEEK_CUR)                  = 184
        read(12, "", 4096)                      = 0
        close(12)                               = 0
        socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 12
        connect(12, {sa_family=AF_INET, sin_port=htons(53), 
sin_addr=inet_addr("192.168.1.1")}, 16) = 0
        gettimeofday({tv_sec=1589546464, tv_usec=72520}, NULL) = 0
        poll([{fd=12, events=POLLOUT}], 1, 0)   = 1 ([{fd=12, revents=POLLOUT}])
        sendto(12, "`\t\1\0\0\1\0\0\0\0\0\0\3gnu\3org\0\0\1\0\1", 25, 
MSG_NOSIGNAL, NULL, 0) = 25
        …

That is, that /etc/resolv.conf had not been reread (there is nothing about it 
in the skipped output above), while the instance that is working fine do check 
whether /etc/resolv.conf is updated:

        …
        stat("/etc/resolv.conf", {st_mode=S_IFREG|0644, st_size=56, ...}) = 0
        openat(AT_FDCWD, "/etc/hosts", O_RDONLY|O_CLOEXEC) = 11
        lseek(11, 0, SEEK_CUR)                  = 0
        fstat(11, {st_mode=S_IFREG|0644, st_size=184, ...}) = 0
        read(11, "127.0.0.1\tlocalhost\n127.0.1.1\tno"..., 4096) = 184
        lseek(11, 0, SEEK_CUR)                  = 184
        read(11, "", 4096)                      = 0
        close(11)                               = 0
        socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, IPPROTO_IP) = 11
        connect(11, {sa_family=AF_INET, sin_port=htons(53), 
sin_addr=inet_addr("192.168.43.223")}, 16) = 0
        gettimeofday({tv_sec=1589546877, tv_usec=860209}, NULL) = 0
        poll([{fd=11, events=POLLOUT}], 1, 0)   = 1 ([{fd=11, revents=POLLOUT}])
        sendmmsg(11, [{msg_hdr={msg_name=NULL, msg_namelen=0, 
msg_iov=[{iov_base="\314\255\1\0\0\1\0\0\0\0\0\0\3gnu\3org\0\0\1\0\1", 
iov_len=25}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, msg_len=25}, 
{msg_hdr={msg_name=NULL, msg_namelen=0, 
msg_iov=[{iov_base="\10\270\1\0\0\1\0\0\0\0\0\0\3gnu\3org\0\0\34\0\1", 
iov_len=25}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, msg_len=25}], 2, 
MSG_NOSIGNAL) = 2
        …

How should I interpret this?

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