Description:
------------
php_tvtoto() in main/php_network.h converts a struct timeval to a timeout in seconds.

In some cases php_tvtoto() is called with a large value for tv_sec, causing the resulting integer to overflow.

For example with mysqlnd, where the default value for mysqlnd.net_read_timeout is 31536000 (one year, in seconds)

poll([{fd=13, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=13, revents=POLLIN}])

#0  0x00007f47000bbe88 in poll () from /lib64/libc.so.6
#1  0x0000000000801399 in php_pollfd_for (stream=<value optimized out>, buf=<value optimized out>, count=<value optimized out>) at /usr/src/php-5.6.17/main/php_network.h:165
#2  php_sockop_write (stream=<value optimized out>, buf=<value optimized out>, count=<value optimized out>) at /usr/src/php-5.6.17/main/streams/xp_socket.c:82
#3  0x000000000047fee0 in php_openssl_sockop_io (read=0, stream=<value optimized out>, buf=<value optimized out>, count=18446744073709551615) at /usr/src/php-5.6.17/ext/openssl/xp_ssl.c:1971
#4  0x00000000007f4457 in _php_stream_write_buffer (stream=0xeadb090, buf=0x148d0780 "e-querylarge-querylarge-querylarge-querylarge-"..., count=25467)
    at /usr/src/php-5.6.17/main/streams/streams.c:1133
#5  0x00000000007c9eec in php_mysqlnd_net_send_ex_pub (net=0x105bb7e0, buffer=0x148cb2a8 "O\270", count=<value optimized out>, conn_stats=<value optimized out>, error_info=<value optimized out>) at /usr/src/php-5.6.17/ext/mysqlnd/mysqlnd_net.c:447
...

31536000 * 1000 mod 2^32 = 1471228928

So poll times out after ~17 days instead of 365 days.

Test script:
---------------
test.php:
<?php
  $db = new mysqli(...);

  // Prepare large query to fill the output buffer causing mysqlnd
  // to call php_pollfd_for()
  $largeSQL = 'SELECT "'. str_repeat('large-query', 1000000) .'"';
  $db->query($largeSQL);
?>

strace test.php

Expected result:
----------------
poll([{fd=4, events=POLLOUT}], 1, 4294967296) = 1 ([{fd=4, revents=POLLOUT}])

(or maybe a timeout of -1 is better)

Actual result:
--------------
poll([{fd=4, events=POLLOUT}], 1, 1471228928) = 1 ([{fd=4, revents=POLLOUT}])