Noticed that one squirrelmail sometime hangs.
It contained default directadmin installation configs.
Straced proccess, and found that it queries DNS servers for a quite long time (only snippet):
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... munmap(0xb7ef5000, 4096) = 0 socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 2108 connect(2108, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0 fcntl64(2108, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(2108, F_SETFL, O_RDWR|O_NONBLOCK) = 0 gettimeofday({1392720955, 282214}, NULL) = 0 poll([{fd=2108, events=POLLOUT}], 1, 0) = 1 ([{fd=2108, revents=POLLOUT}]) send(2108, "H\177\1\0\0\1\0\0\0\0\0\0\00248\003177\003231\003173\tspam"..., 54, MSG_NOSIGNAL) = 54 poll([{fd=2108, events=POLLIN}], 1, 5000) = 1 ([{fd=2108, revents=POLLIN}]) ioctl(2108, FIONREAD, [104]) = 0 recvfrom(2108, "H\177\201\203\0\1\0\0\0\1\0\0\00248\003177\003231\003173\tspam"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, [16]) = 104 close(2108) = 0 time(NULL) = 1392720955 open("/etc/hosts", O_RDONLY) = 2108 fcntl64(2108, F_GETFD) = 0 fcntl64(2108, F_SETFD, FD_CLOEXEC) = 0 fstat64(2108, {st_mode=S_IFREG|0644, st_size=273, ...}) = 0 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ef5000 read(2108, "# Do not remove the following li"..., 4096) = 273 read(2108, "", 4096) = 0 close(2108) = 0 munmap(0xb7ef5000, 4096) = 0 socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 2108 connect(2108, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0 fcntl64(2108, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(2108, F_SETFL, O_RDWR|O_NONBLOCK) = 0 gettimeofday({1392720955, 396610}, NULL) = 0 poll([{fd=2108, events=POLLOUT}], 1, 0) = 1 ([{fd=2108, revents=POLLOUT}]) send(2108, "\242Z\1\0\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 48, MSG_NOSIGNAL) = 48 poll([{fd=2108, events=POLLIN}], 1, 5000) = 0 (Timeout) socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 2109 connect(2109, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")}, 28) = 0 fcntl64(2109, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(2109, F_SETFL, O_RDWR|O_NONBLOCK) = 0 gettimeofday({1392720960, 396031}, NULL) = 0 poll([{fd=2109, events=POLLOUT}], 1, 0) = 1 ([{fd=2109, revents=POLLOUT}]) send(2109, "\242Z\1\0\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 48, MSG_NOSIGNAL) = 48 poll([{fd=2109, events=POLLIN}], 1, 3000) = 0 (Timeout) socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 2110 connect(2110, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.4.4")}, 28) = 0 fcntl64(2110, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(2110, F_SETFL, O_RDWR|O_NONBLOCK) = 0 gettimeofday({1392720963, 399893}, NULL) = 0 poll([{fd=2110, events=POLLOUT}], 1, 0) = 1 ([{fd=2110, revents=POLLOUT}]) send(2110, "\242Z\1\0\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 48, MSG_NOSIGNAL) = 48 poll([{fd=2110, events=POLLIN}], 1, 6000) = 1 ([{fd=2110, revents=POLLIN}]) ioctl(2110, FIONREAD, [48]) = 0 recvfrom(2110, "\242Z\201\202\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.4.4")}, [16]) = 48 close(2108) = 0 close(2109) = 0 close(2110) = 0 socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 2108 connect(2108, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("127.0.0.1")}, 28) = 0 fcntl64(2108, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(2108, F_SETFL, O_RDWR|O_NONBLOCK) = 0 gettimeofday({1392720968, 243445}, NULL) = 0 poll([{fd=2108, events=POLLOUT}], 1, 0) = 1 ([{fd=2108, revents=POLLOUT}]) send(2108, "\242Z\1\0\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 48, MSG_NOSIGNAL) = 48 poll([{fd=2108, events=POLLIN}], 1, 5000) = 0 (Timeout) socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 2109 connect(2109, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.8.8")}, 28) = 0 fcntl64(2109, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(2109, F_SETFL, O_RDWR|O_NONBLOCK) = 0 gettimeofday({1392720973, 266865}, NULL) = 0 poll([{fd=2109, events=POLLOUT}], 1, 0) = 1 ([{fd=2109, revents=POLLOUT}]) send(2109, "\242Z\1\0\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 48, MSG_NOSIGNAL) = 48 poll([{fd=2109, events=POLLIN}], 1, 3000) = 0 (Timeout) socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 2110 connect(2110, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.4.4")}, 28) = 0 fcntl64(2110, F_GETFL) = 0x2 (flags O_RDWR) fcntl64(2110, F_SETFL, O_RDWR|O_NONBLOCK) = 0 gettimeofday({1392720976, 278949}, NULL) = 0 poll([{fd=2110, events=POLLOUT}], 1, 0) = 1 ([{fd=2110, revents=POLLOUT}]) send(2110, "\242Z\1\0\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 48, MSG_NOSIGNAL) = 48 poll([{fd=2110, events=POLLIN}], 1, 6000) = 1 ([{fd=2110, revents=POLLIN}]) ioctl(2110, FIONREAD, [48]) = 0 recvfrom(2110, "\242Z\201\202\0\1\0\0\0\0\0\0\00248\003177\003231\003173\5dnsb"..., 1024, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("8.8.4.4")}, [16]) = 48 ... |
After “querying” for some time, it generated file:
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/var/www/html/squirrelmail/data/dnscache |
As quick investigation revealed, it’s squirrelmail spam filter enabled by directadmin:
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$plugins[1] = 'filters'; |
It contains old and already non working blacklist links, for spam control.
Found README file of current squirrelmail version spam plugin here
Snippet from README:
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This is a poor alternative to procmail or Elm's filter programs. This is a pathetic replacement for good RBL mail scanning when you get the mail. This is more for systems that can't/won't offer that kind of functionality and you still require it. This is slow. Yep. Slow. |
So my advice would be just to disable this plugin and use other filters on server.
With directadmin there is perfect spam filter: spamassassin, or You may add blacklist filters straight to Your mail transfer agent (most used postfix and exim have this feature).
If there is a question how to disable it, here is example (default directadmin squirrelmail config):
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$plugins[0] = 'spamcop'; $plugins[1] = 'filters'; $plugins[2] = 'squirrelspell'; |
make to:
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$plugins[0] = 'spamcop'; $plugins[1] = 'squirrelspell'; |
Problem solved
