do not expose recvmmsg/sendmmsg for unsupported kernels

libc/inet/socketcalls.c

@@ -8,6 +8,7 @@
 #include <sys/syscall.h>
 #include <sys/socket.h>
 #include <cancel.h>
+#include <bits/kernel-features.h>
 
 #ifdef __NR_socketcall
 /* Various socketcall numbers */
@@ -267,6 +268,7 @@ lt_libc_hidden(recvmsg)
 #endif
 
 #ifdef L_recvmmsg
+#ifdef __ASSUME_RECVMMSG_SYSCALL
 static ssize_t __NC(recvmmsg)(int sockfd, struct mmsghdr *msg, size_t vlen,
 			      int flags, struct timespec *tmo)
 {
@@ -289,6 +291,7 @@ CANCELLABLE_SYSCALL(ssize_t, recvmmsg,
 		    (sockfd, msg, vlen, flags, tmo))
 lt_libc_hidden(recvmmsg)
 #endif
+#endif
 
 #ifdef L_send
 static ssize_t __NC(send)(int sockfd, const void *buffer, size_t len, int flags)
@@ -332,6 +335,7 @@ lt_libc_hidden(sendmsg)
 #endif
 
 #ifdef L_sendmmsg
+#ifdef __ASSUME_SENDMMSG_SYSCALL
 static ssize_t __NC(sendmmsg)(int sockfd, struct mmsghdr *msg, size_t vlen,
 			      int flags)
 {
@@ -352,6 +356,7 @@ CANCELLABLE_SYSCALL(ssize_t, sendmmsg,
 		    (sockfd, msg, vlen, flags))
 lt_libc_hidden(sendmmsg)
 #endif
+#endif
 
 #ifdef L_sendto
 ssize_t __NC(sendto)(int sockfd, const void *buffer, size_t len, int flags,

libc/sysdeps/linux/common/bits/kernel-features.h

@@ -461,6 +461,12 @@
 # define __ASSUME_ACCEPT4       1
 #endif
 
+/* Support for the recvmmsg/sendmmsg syscall was added in 2.6.33  */
+#if __LINUX_KERNEL_VERSION >= 0x020621
+#define __ASSUME_RECVMMSG_SYSCALL       1
+#define __ASSUME_SENDMMSG_SYSCALL       1
+#endif
+
 /* Support for the FUTEX_CLOCK_REALTIME flag was added in 2.6.29.  */
 #if __LINUX_KERNEL_VERSION >= 0x02061d
 # define __ASSUME_FUTEX_CLOCK_REALTIME	1