ntp: rework receiving messages

Allocate buffers for received messages on heap instead of stack and
prepare the code for receiving multiple messages at the same time.

ntp_io.c

@@ -30,6 +30,7 @@
 
 #include "sysincl.h"
 
+#include "array.h"
 #include "ntp_io.h"
 #include "ntp_core.h"
 #include "ntp_sources.h"
@@ -51,6 +52,25 @@ union sockaddr_in46 {
   struct sockaddr u;
 };
 
+struct Message {
+  union sockaddr_in46 name;
+  struct iovec iov;
+  NTP_Receive_Buffer buf;
+  /* Aligned buffer for control messages */
+  struct cmsghdr cmsgbuf[CMSGBUF_SIZE / sizeof (struct cmsghdr)];
+};
+
+struct MessageHeader {
+  struct msghdr msg_hdr;
+  unsigned int msg_len;
+};
+
+#define MAX_RECV_MESSAGES 1
+
+/* Arrays of Message and MessageHeader */
+static ARR_Instance recv_messages;
+static ARR_Instance recv_headers;
+
 /* The server/peer and client sockets for IPv4 and IPv6 */
 static int server_sock_fd4;
 static int client_sock_fd4;
@@ -288,6 +308,33 @@ close_socket(int sock_fd)
 }
 
 /* ================================================== */
+
+static void
+prepare_buffers(unsigned int n)
+{
+  struct MessageHeader *hdr;
+  struct Message *msg;
+  unsigned int i;
+
+  for (i = 0; i < n; i++) {
+    msg = ARR_GetElement(recv_messages, i);
+    hdr = ARR_GetElement(recv_headers, i);
+
+    msg->iov.iov_base = &msg->buf;
+    msg->iov.iov_len = sizeof (msg->buf);
+    hdr->msg_hdr.msg_name = &msg->name;
+    hdr->msg_hdr.msg_namelen = sizeof (msg->name);
+    hdr->msg_hdr.msg_iov = &msg->iov;
+    hdr->msg_hdr.msg_iovlen = 1;
+    hdr->msg_hdr.msg_control = &msg->cmsgbuf;
+    hdr->msg_hdr.msg_controllen = sizeof (msg->cmsgbuf);
+    hdr->msg_hdr.msg_flags = 0;
+    hdr->msg_len = 0;
+  }
+}
+
+/* ================================================== */
+
 void
 NIO_Initialise(int family)
 {
@@ -296,6 +343,12 @@ NIO_Initialise(int family)
   assert(!initialised);
   initialised = 1;
 
+  recv_messages = ARR_CreateInstance(sizeof (struct Message));
+  ARR_SetSize(recv_messages, MAX_RECV_MESSAGES);
+  recv_headers = ARR_CreateInstance(sizeof (struct MessageHeader));
+  ARR_SetSize(recv_headers, MAX_RECV_MESSAGES);
+  prepare_buffers(MAX_RECV_MESSAGES);
+
   server_port = CNF_GetNTPPort();
   client_port = CNF_GetAcquisitionPort();
 
@@ -368,6 +421,8 @@ NIO_Finalise(void)
   close_socket(server_sock_fd6);
   server_sock_fd6 = client_sock_fd6 = INVALID_SOCK_FD;
 #endif
+  ARR_DestroyInstance(recv_headers);
+  ARR_DestroyInstance(recv_messages);
   initialised = 0;
 }
 
@@ -483,57 +538,28 @@ NIO_IsServerSocket(int sock_fd)
 /* ================================================== */
 
 static void
-read_from_socket(int sock_fd, int event, void *anything)
+process_receive(struct msghdr *hdr, int length, int sock_fd)
 {
-  /* This should only be called when there is something
-     to read, otherwise it will block. */
-
-  int status;
-  NTP_Receive_Buffer message;
-  union sockaddr_in46 where_from;
-  unsigned int flags = 0;
-  struct timeval now;
-  double now_err;
   NTP_Remote_Address remote_addr;
   NTP_Local_Address local_addr;
-  struct cmsghdr cmsgbuf[CMSGBUF_SIZE / sizeof (struct cmsghdr)];
-  struct msghdr msg;
-  struct iovec iov;
   struct cmsghdr *cmsg;
-
+  struct timeval now;
-  assert(initialised);
+  double now_err;
 
   SCH_GetLastEventTime(&now, &now_err, NULL);
 
-  iov.iov_base = &message.ntp_pkt;
+  if (hdr->msg_namelen > sizeof (union sockaddr_in46)) {
-  iov.iov_len = sizeof(message);
+    DEBUG_LOG(LOGF_NtpIO, "Truncated source address");
-  msg.msg_name = &where_from;
+    return;
-  msg.msg_namelen = sizeof(where_from);
+  }
-  msg.msg_iov = &iov;
-  msg.msg_iovlen = 1;
-  msg.msg_control = (void *) cmsgbuf;
-  msg.msg_controllen = sizeof(cmsgbuf);
-  msg.msg_flags = 0;
 
-  status = recvmsg(sock_fd, &msg, flags);
+  UTI_SockaddrToIPAndPort((struct sockaddr *)hdr->msg_name,
-
+                          &remote_addr.ip_addr, &remote_addr.port);
-  /* Don't bother checking if read failed or why if it did.  More
-     likely than not, it will be connection refused, resulting from a
-     previous sendto() directing a datagram at a port that is not
-     listening (which appears to generate an ICMP response, and on
-     some architectures e.g. Linux this is translated into an error
-     reponse on a subsequent recvfrom). */
-
-  if (status > 0) {
-    if (msg.msg_namelen > sizeof (where_from))
-      LOG_FATAL(LOGF_NtpIO, "Truncated source address");
-
-    UTI_SockaddrToIPAndPort(&where_from.u, &remote_addr.ip_addr, &remote_addr.port);
 
   local_addr.ip_addr.family = IPADDR_UNSPEC;
   local_addr.sock_fd = sock_fd;
 
-    for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+  for (cmsg = CMSG_FIRSTHDR(hdr); cmsg; cmsg = CMSG_NXTHDR(hdr, cmsg)) {
 #ifdef HAVE_IN_PKTINFO
     if (cmsg->cmsg_level == IPPROTO_IP && cmsg->cmsg_type == IP_PKTINFO) {
       struct in_pktinfo ipi;
@@ -566,20 +592,51 @@ read_from_socket(int sock_fd, int event, void *anything)
   }
 
   DEBUG_LOG(LOGF_NtpIO, "Received %d bytes from %s:%d to %s fd %d",
-              status, UTI_IPToString(&remote_addr.ip_addr), remote_addr.port,
+            length, UTI_IPToString(&remote_addr.ip_addr), remote_addr.port,
             UTI_IPToString(&local_addr.ip_addr), local_addr.sock_fd);
 
-    if (status >= NTP_NORMAL_PACKET_LENGTH) {
-
-      NSR_ProcessReceive((NTP_Packet *) &message.ntp_pkt, &now, now_err,
-                         &remote_addr, &local_addr, status);
-
-    } else {
-
   /* Just ignore the packet if it's not of a recognized length */
+  if (length < NTP_NORMAL_PACKET_LENGTH || length > sizeof (NTP_Receive_Buffer))
+    return;
 
+  NSR_ProcessReceive((NTP_Packet *)hdr->msg_iov[0].iov_base, &now, now_err,
+                     &remote_addr, &local_addr, length);
+}
+
+/* ================================================== */
+
+static void
+read_from_socket(int sock_fd, int event, void *anything)
+{
+  /* This should only be called when there is something
+     to read, otherwise it will block */
+
+  struct MessageHeader *hdr;
+  unsigned int i, n;
+  int status;
+
+  hdr = ARR_GetElements(recv_headers);
+  n = ARR_GetSize(recv_headers);
+  assert(n >= 1);
+
+  n = 1;
+  status = recvmsg(sock_fd, &hdr[0].msg_hdr, 0);
+  if (status >= 0)
+    hdr[0].msg_len = status;
+
+  if (status < 0) {
+    DEBUG_LOG(LOGF_NtpIO, "Could not receive from fd %d : %s", sock_fd,
+              strerror(errno));
+    return;
   }
+
+  for (i = 0; i < n; i++) {
+    hdr = ARR_GetElement(recv_headers, i);
+    process_receive(&hdr->msg_hdr, hdr->msg_len, sock_fd);
   }
+
+  /* Restore the buffers to their original state */
+  prepare_buffers(n);
 }
 
 /* ================================================== */