BUG/MEDIUM: listener: improve detection of non-working accept4()
On ARM, glibc does not implement accept4() and simply returns ENOSYS
which was not caught as a reason to fall back to accept(), resulting
in a spinning process since poll() would call again.
Let's change the error detection mechanism to save the broken status
of the syscall into a local variable that is used to fall back to the
legacy accept().
In addition to this, since the code was becoming a bit messy, the
accept4() was removed, so now the fallback code and the legacy code
are the same. This will also increase bug report accuracy if needed.
This is 1.5-specific, no backport is needed.
diff --git a/src/listener.c b/src/listener.c
index 1ce35de..05bb743 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -257,6 +257,9 @@
int max_accept = l->maxaccept ? l->maxaccept : 1;
int cfd;
int ret;
+#ifdef USE_ACCEPT4
+ static int accept4_broken;
+#endif
if (unlikely(l->nbconn >= l->maxconn)) {
listener_full(l);
@@ -346,15 +349,17 @@
}
#ifdef USE_ACCEPT4
- cfd = accept4(fd, (struct sockaddr *)&addr, &laddr, SOCK_NONBLOCK);
- if (unlikely(cfd == -1 && errno == EINVAL)) {
- /* unsupported syscall, fallback to normal accept()+fcntl() */
+ /* only call accept4() if it's known to be safe, otherwise
+ * fallback to the legacy accept() + fcntl().
+ */
+ if (unlikely(accept4_broken ||
+ ((cfd = accept4(fd, (struct sockaddr *)&addr, &laddr, SOCK_NONBLOCK)) == -1 &&
+ (errno == ENOSYS || errno == EINVAL || errno == EBADF) &&
+ (accept4_broken = 1))))
+#endif
if ((cfd = accept(fd, (struct sockaddr *)&addr, &laddr)) != -1)
fcntl(cfd, F_SETFL, O_NONBLOCK);
- }
-#else
- cfd = accept(fd, (struct sockaddr *)&addr, &laddr);
-#endif
+
if (unlikely(cfd == -1)) {
switch (errno) {
case EAGAIN:
diff --git a/src/session.c b/src/session.c
index 1faf0c3..aae0c69 100644
--- a/src/session.c
+++ b/src/session.c
@@ -148,14 +148,6 @@
goto out_free_session;
}
-#ifndef USE_ACCEPT4
- /* Adjust some socket options if the connection was accepted by a plain
- * accept() syscall.
- */
- if (unlikely(fcntl(cfd, F_SETFL, O_NONBLOCK) == -1))
- goto out_free_session;
-#endif
-
/* monitor-net and health mode are processed immediately after TCP
* connection rules. This way it's possible to block them, but they
* never use the lower data layers, they send directly over the socket,