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Commitbfc9497

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libpq: Use modern socket flags, if available.
Since commit7627b91, libpq has used FD_CLOEXEC so that socketswouldn't be leaked to subprograms. With enough bad luck, amulti-threaded program might fork in between the socket() and fcntl()calls. We can close that tiny gap by using SOCK_CLOEXEC instead of aseparate call. While here, we might as well do the same forSOCK_NONBLOCK, to save another syscall.These flags are expected to appear in the next revision of the POSIXstandard, specifically to address this problem. Our Unixoid targetsexcept macOS and AIX have had them for a long time, and macOS wouldhopefully use guarded availability to roll them out, so it seems enoughto use a simple ifdef test for availability until we hear otherwise.Windows doesn't have them, but has non-inheritable sockets by default.Discussion:https://postgr.es/m/CA%2BhUKGKb6FsAdQWcRL35KJsftv%2B9zXqQbzwkfRf1i0J2e57%2BhQ%40mail.gmail.com
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‎src/interfaces/libpq/fe-connect.c

Lines changed: 25 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2629,6 +2629,7 @@ PQconnectPoll(PGconn *conn)
26292629
{
26302630
structaddrinfo*addr_cur=conn->addr_cur;
26312631
charhost_addr[NI_MAXHOST];
2632+
intsock_type;
26322633

26332634
/*
26342635
* Advance to next possible host, if we've tried all of
@@ -2659,7 +2660,26 @@ PQconnectPoll(PGconn *conn)
26592660
conn->connip=strdup(host_addr);
26602661

26612662
/* Try to create the socket */
2662-
conn->sock=socket(addr_cur->ai_family,SOCK_STREAM,0);
2663+
sock_type=SOCK_STREAM;
2664+
#ifdefSOCK_CLOEXEC
2665+
2666+
/*
2667+
* Atomically mark close-on-exec, if possible on this
2668+
* platform, so that there isn't a window where a
2669+
* subprogram executed by another thread inherits the
2670+
* socket. See fallback code below.
2671+
*/
2672+
sock_type |=SOCK_CLOEXEC;
2673+
#endif
2674+
#ifdefSOCK_NONBLOCK
2675+
2676+
/*
2677+
* We might as well skip a system call for nonblocking
2678+
* mode too, if we can.
2679+
*/
2680+
sock_type |=SOCK_NONBLOCK;
2681+
#endif
2682+
conn->sock=socket(addr_cur->ai_family,sock_type,0);
26632683
if (conn->sock==PGINVALID_SOCKET)
26642684
{
26652685
interrorno=SOCK_ERRNO;
@@ -2705,14 +2725,17 @@ PQconnectPoll(PGconn *conn)
27052725
gotokeep_going;
27062726
}
27072727
}
2728+
#ifndefSOCK_NONBLOCK
27082729
if (!pg_set_noblock(conn->sock))
27092730
{
27102731
libpq_append_conn_error(conn,"could not set socket to nonblocking mode: %s",
27112732
SOCK_STRERROR(SOCK_ERRNO,sebuf,sizeof(sebuf)));
27122733
conn->try_next_addr= true;
27132734
gotokeep_going;
27142735
}
2736+
#endif
27152737

2738+
#ifndefSOCK_CLOEXEC
27162739
#ifdefF_SETFD
27172740
if (fcntl(conn->sock,F_SETFD,FD_CLOEXEC)==-1)
27182741
{
@@ -2722,6 +2745,7 @@ PQconnectPoll(PGconn *conn)
27222745
gotokeep_going;
27232746
}
27242747
#endif/* F_SETFD */
2748+
#endif
27252749

27262750
if (addr_cur->ai_family!=AF_UNIX)
27272751
{

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