Fix #12, support sendmmsg for UDP

Makefile

@@ -189,6 +189,10 @@ OTHER_FLAGS = -Wall
 ifeq ($(shell test -f /usr/include/sys/epoll.h && echo yes), yes)
 DEFINES     += -DMD_HAVE_EPOLL
 endif
+# For SRS, sendmmsg
+ifeq ($(shell grep -qs sendmmsg /usr/include/sys/socket.h && echo yes), yes)
+DEFINES     += -DMD_HAVE_SENDMMSG -D_GNU_SOURCE
+endif
 endif
 
 ifeq ($(OS), NETBSD)
@@ -282,6 +286,10 @@ endif
 #
 # make EXTRA_CFLAGS=-UMD_HAVE_EPOLL <target>
 #
+# or to enable sendmmsg(2) support:
+#
+# make EXTRA_CFLAGS="-DMD_HAVE_SENDMMSG -D_GNU_SOURCE"
+#
 ##########################
 
 CFLAGS      += $(DEFINES) $(OTHER_FLAGS) $(EXTRA_CFLAGS)

README.md

@@ -23,6 +23,7 @@ The branch [srs](https://github.com/ossrs/state-threads/tree/srs) will be patche
 - [x] Support macro `MD_ST_NO_ASM` to disable ASM, [#8](https://github.com/ossrs/state-threads/issues/8).
 - [x] Merge patch [srs#1282](https://github.com/ossrs/srs/issues/1282#issuecomment-445539513) to support aarch64, [#9](https://github.com/ossrs/state-threads/issues/9).
 - [x] Support OSX for Apple Darwin, macOS, [#11](https://github.com/ossrs/state-threads/issues/11).
+- [x] Support sendmmsg for UDP, [#12](https://github.com/ossrs/state-threads/issues/12).
 
 ## Docs
 
@@ -86,4 +87,10 @@ Important cli options:
 1. `--track-origins=<yes|no> [default: no]`, Controls whether Memcheck tracks the origin of uninitialised values. By default, it does not, which means that although it can tell you that an uninitialised value is being used in a dangerous way, it cannot tell you where the uninitialised value came from. This often makes it difficult to track down the root problem.
 1. `--show-reachable=<yes|no> , --show-possibly-lost=<yes|no>`, to show the using memory.
 
+## Analysis
+
+1. About setjmp and longjmp, read [setjmp](https://gitee.com/winlinvip/srs-wiki/raw/master/images/st-setjmp.jpg).
+1. About the stack structure, read [stack](https://gitee.com/winlinvip/srs-wiki/raw/master/images/st-stack.jpg)
+1. About asm code comments, read [#91d530e](https://github.com/ossrs/state-threads/commit/91d530e#diff-ed9428b14ff6afda0e9ab04cc91d4445R25).
+
 Winlin 2016

io.c

@@ -743,6 +743,38 @@ int st_sendmsg(_st_netfd_t *fd, const struct msghdr *msg, int flags, st_utime_t
 }
 
 
+#if defined(MD_HAVE_SENDMMSG) && defined(_GNU_SOURCE)
+int st_sendmmsg(st_netfd_t fd, struct mmsghdr *msgvec, unsigned int vlen, int flags, st_utime_t timeout)
+{
+    int n;
+    int left;
+    struct mmsghdr *p;
+
+    left = (int)vlen;
+    while (left > 0) {
+        p = msgvec + (vlen - left);
+
+        if ((n = sendmmsg(fd->osfd, p, left, flags)) < 0) {
+            if (errno == EINTR)
+                continue;
+            if (!_IO_NOT_READY_ERROR)
+                break;
+            /* Wait until the socket becomes writable */
+            if (st_netfd_poll(fd, POLLOUT, timeout) < 0)
+                break;
+        }
+
+        left -= n;
+    }
+
+    // An error is returned only if no datagrams could be sent.
+    if (left == (int)vlen) {
+        return n;
+    }
+    return (int)vlen - left;
+}
+#endif
+
 
 /*
  * To open FIFOs or other special files.

public.h

@@ -151,6 +151,7 @@ extern int st_recvfrom(st_netfd_t fd, void *buf, int len, struct sockaddr *from,
 extern int st_sendto(st_netfd_t fd, const void *msg, int len, const struct sockaddr *to, int tolen, st_utime_t timeout);
 extern int st_recvmsg(st_netfd_t fd, struct msghdr *msg, int flags, st_utime_t timeout);
 extern int st_sendmsg(st_netfd_t fd, const struct msghdr *msg, int flags, st_utime_t timeout);
+extern int st_sendmmsg(st_netfd_t fd, struct mmsghdr *msgvec, unsigned int vlen, int flags, st_utime_t timeout);
 extern st_netfd_t st_open(const char *path, int oflags, mode_t mode);
 
 #ifdef DEBUG