udp-handler: simplify recvmmsg/sendmmsg detection

configure.ac

@@ -123,27 +123,21 @@ PKG_CHECK_MODULES([gnutls], [gnutls >= 3.3 nettle], [
 # JSON for DNSSEC status storage
 PKG_CHECK_MODULES([jansson], [jansson >= 2.3])
 
-# recvmmsg() (valgrind doesn't support it, so disable for debugging)
-# The check for struct mmsghdr is required when libc doesn't have an API but the function links
 AC_ARG_ENABLE([recvmmsg],
-    AS_HELP_STRING([--enable-recvmmsg=yes|no], [enable recvmmsg() network API under Linux (kernel support required) (set to 'no' if you have trouble running server under valgrind) [default=yes]]),
-    [case "${enableval}" in
-      yes)
-          AC_CHECK_FUNCS([sendmmsg])
-          AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <sys/socket.h>]], [[struct mmsghdr v; recvmmsg(0,0,0,0,0);]])],
-          [AC_DEFINE(HAVE_RECVMMSG, 1, [Define if struct mmsghdr and recvmmsg() exists.])])
-          ;;
-      no)
-          ;;
-      *)
-          AC_MSG_ERROR([bad value ${enableval} for --enable-recvmmsg])
-          ;;
-    esac],
-    [
-      AC_CHECK_FUNCS([sendmmsg])
-      AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <sys/socket.h>]], [[struct mmsghdr v; recvmmsg(0,0,0,0,0);]])],
-      [AC_DEFINE(HAVE_RECVMMSG, 1, [Define if struct mmsghdr and recvmmsg() exists.])])
-    ])
+   AS_HELP_STRING([--enable-recvmmsg=auto|yes|no], [enable recvmmsg() network API [default=auto]]),
+   [], [enable_recvmmsg=auto])
+
+AS_CASE([$enable_recvmmsg],
+   [auto|yes],[
+      AC_CHECK_FUNC([recvmmsg],
+                    [AC_CHECK_FUNC([sendmmsg],[enable_recvmmsg=yes],[enable_recvmmsg=no])],
+                    [enable_recvmmsg=no])],
+   [no],[],
+   [*], [AC_MSG_ERROR([Invalid value of --enable-recvmmsg.]
+ )])
+
+AS_IF([test "$enable_recvmmsg" = yes],[
+   AC_DEFINE([ENABLE_RECVMMSG], [1], [Use recvmmsg().])])
 
 AC_ARG_ENABLE([reuseport],
     AS_HELP_STRING([--enable-reuseport=auto|yes|no], [enable Linux SO_REUSEPORT support [default=auto]]),
@@ -572,6 +566,7 @@ AC_MSG_RESULT([
     Knot DNS utils:         ${enable_utilities}
     Knot DNS documentation: ${enable_documentation}
 
+    Use recvmmsg:        ${enable_recvmmsg}
     Use SO_REUSEPORT:    ${enable_reuseport}
     Fast zone parser:    ${enable_fastparser}
     Utilities with IDN:  ${with_libidn}

src/knot/server/udp-handler.c

@@ -21,7 +21,6 @@
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
-#include <sys/syscall.h>
 #include <string.h>
 #include <assert.h>
 #include <sys/param.h>
@@ -105,15 +104,6 @@ static void udp_handle(udp_context_t *udp, int fd, struct sockaddr_storage *ss,
 	knot_pkt_free(&ans);
 }
 
-/* Check for sendmmsg syscall. */
-#ifdef HAVE_SENDMMSG
-  #define ENABLE_SENDMMSG 1
-#else
-  #ifdef SYS_sendmmsg
-    #define ENABLE_SENDMMSG 1
-  #endif
-#endif
-
 /*! \brief Pointer to selected UDP master implementation. */
 static void* (*_udp_init)(void) = 0;
 static int (*_udp_deinit)(void *) = 0;
@@ -239,49 +229,7 @@ static int udp_recvfrom_send(void *d)
 	return 0;
 }
 
-#ifdef HAVE_RECVMMSG
-
-/*! \brief Pointer to selected UDP send implementation. */
-static int (*_send_mmsg)(int, struct sockaddr *, struct mmsghdr *, size_t) = 0;
-
-/*!
- * \brief Send multiple packets.
- *
- * Basic, sendmsg() based implementation.
- */
-static int udp_sendmsg(int sock, struct sockaddr *addrs, struct mmsghdr *msgs, size_t count)
-{
-	int sent = 0;
-	for (unsigned i = 0; i < count; ++i) {
-		if (sendmsg(sock, &msgs[i].msg_hdr, 0) > 0) {
-			++sent;
-		}
-	}
-
-	return sent;
-}
-
-#ifdef ENABLE_SENDMMSG
-/*! \brief sendmmsg() syscall interface. */
-#ifndef HAVE_SENDMMSG
-static inline int sendmmsg(int fd, struct mmsghdr *mmsg, unsigned vlen,
-                           unsigned flags)
-{
-	return syscall(SYS_sendmmsg, fd, mmsg, vlen, flags, NULL);
-}
-#endif /* HAVE_SENDMMSG */
-
-/*!
- * \brief Send multiple packets.
- *
- * sendmmsg() implementation.
- */
-static int udp_sendmmsg(int sock, struct sockaddr *_, struct mmsghdr *msgs, size_t count)
-{
-	UNUSED(_);
-	return sendmmsg(sock, msgs, count, 0);
-}
-#endif /* ENABLE_SENDMMSG */
+#ifdef ENABLE_RECVMMSG
 
 /* UDP recvmmsg() request struct. */
 struct udp_recvmmsg {
@@ -374,7 +322,7 @@ static int udp_recvmmsg_handle(udp_context_t *ctx, void *d)
 static int udp_recvmmsg_send(void *d)
 {
 	struct udp_recvmmsg *rq = (struct udp_recvmmsg *)d;
-	int rc = _send_mmsg(rq->fd, (struct sockaddr *)rq->addrs, rq->msgs[TX], rq->rcvd);
+	int rc = sendmmsg(rq->fd, rq->msgs[TX], rq->rcvd, 0);
 	for (unsigned i = 0; i < rq->rcvd; ++i) {
 		/* Reset buffer size and address len. */
 		struct iovec *rx = rq->msgs[RX][i].msg_hdr.msg_iov;
@@ -389,38 +337,25 @@ static int udp_recvmmsg_send(void *d)
 	}
 	return rc;
 }
-#endif /* HAVE_RECVMMSG */
+#endif /* ENABLE_RECVMMSG */
 
 /*! \brief Initialize UDP master routine on run-time. */
 void __attribute__ ((constructor)) udp_master_init(void)
 {
 	/* Initialize defaults. */
-	_udp_init = udp_recvfrom_init;
+	_udp_init =   udp_recvfrom_init;
 	_udp_deinit = udp_recvfrom_deinit;
-	_udp_recv = udp_recvfrom_recv;
-	_udp_send = udp_recvfrom_send;
+	_udp_recv =   udp_recvfrom_recv;
 	_udp_handle = udp_recvfrom_handle;
-
-	/* Optimized functions. */
-#ifdef HAVE_RECVMMSG
-	recvmmsg(0, NULL, 0, 0, 0);
-	if (errno != ENOSYS) {
-		_udp_init = udp_recvmmsg_init;
-		_udp_deinit = udp_recvmmsg_deinit;
-		_udp_recv = udp_recvmmsg_recv;
-		_udp_send = udp_recvmmsg_send;
-		_udp_handle = udp_recvmmsg_handle;
-	}
-
-	/* Check for sendmmsg() support. */
-	_send_mmsg = udp_sendmsg;
-#ifdef ENABLE_SENDMMSG
-	sendmmsg(0, 0, 0, 0); /* Just check if syscall exists */
-	if (errno != ENOSYS) {
-		_send_mmsg = udp_sendmmsg;
-	}
-#endif /* ENABLE_SENDMMSG */
-#endif /* HAVE_RECVMMSG */
+	_udp_send =   udp_recvfrom_send;
+
+#ifdef ENABLE_RECVMMSG
+	_udp_init =   udp_recvmmsg_init;
+	_udp_deinit = udp_recvmmsg_deinit;
+	_udp_recv =   udp_recvmmsg_recv;
+	_udp_handle = udp_recvmmsg_handle;
+	_udp_send =   udp_recvmmsg_send;
+#endif /* ENABLE_RECVMMSG */
 }
 
 /*! \brief Get interface UDP descriptor for a given thread. */