Add alternate timestamp implementations

Add mach_absolute_time and gettimeofday timestamp implementations, and
fix clock_gettime check so that it can actually succeed

configure.ac

@@ -70,7 +70,14 @@ AC_FUNC_FORK
 AC_FUNC_MALLOC
 AC_FUNC_MBRTOWC
 AC_FUNC_REALLOC
-AC_CHECK_FUNCS([clock_gettime gettimeofday inet_ntoa iswprint memchr memset nl_langinfo setenv setlocale socket strchr strdup strerror strtol wcwidth])
+AC_CHECK_FUNCS([gettimeofday inet_ntoa iswprint memchr memset nl_langinfo setenv setlocale socket strchr strdup strerror strtol wcwidth])
+
+AC_SEARCH_LIBS([clock_gettime], [rt], [AC_DEFINE([HAVE_CLOCK_GETTIME], [1], [Define if clock_gettime is available.])])
+
+AC_CHECK_DECL([mach_absolute_time],
+  [AC_DEFINE([HAVE_MACH_ABSOLUTE_TIME], [1],
+     [Define if mach_absolute_time is available.])],
+  , [[#include <mach/mach_time.h>]])
 
 AC_CHECK_DECL([htobe64],
   [AC_DEFINE([HAVE_HTOBE64], [1],

src/examples/Makefile.am

@@ -20,4 +20,4 @@ termemu_LDADD = ../terminal/libmoshterminal.a ../util/libmoshutil.a ../statesync
 
 ntester_SOURCES = ntester.cc
 ntester_CPPFLAGS = -I$(srcdir)/../statesync -I$(srcdir)/../terminal -I$(srcdir)/../network -I$(srcdir)/../crypto -I$(builddir)/../protobufs
-ntester_LDADD = ../statesync/libmoshstatesync.a ../terminal/libmoshterminal.a ../network/libmoshnetwork.a ../crypto/libmoshcrypto.a ../protobufs/libmoshprotos.a -lutil -lrt -lm $(protobuf_LIBS)
+ntester_LDADD = ../statesync/libmoshstatesync.a ../terminal/libmoshterminal.a ../network/libmoshnetwork.a ../crypto/libmoshcrypto.a ../protobufs/libmoshprotos.a -lutil -lm $(protobuf_LIBS)

src/frontend/Makefile.am

@@ -1,6 +1,6 @@
 AM_CPPFLAGS = -I$(srcdir)/../statesync -I$(srcdir)/../terminal -I$(srcdir)/../network -I$(srcdir)/../crypto -I$(builddir)/../protobufs -I$(srcdir)/../util
 AM_CXXFLAGS = $(WARNING_CXXFLAGS) $(PICKY_CXXFLAGS) -fno-default-inline -pipe
-LDADD = ../crypto/libmoshcrypto.a ../network/libmoshnetwork.a ../statesync/libmoshstatesync.a ../terminal/libmoshterminal.a ../util/libmoshutil.a ../protobufs/libmoshprotos.a -lutil -lrt -lm $(protobuf_LIBS)
+LDADD = ../crypto/libmoshcrypto.a ../network/libmoshnetwork.a ../statesync/libmoshstatesync.a ../terminal/libmoshterminal.a ../util/libmoshutil.a ../protobufs/libmoshprotos.a -lutil -lm $(protobuf_LIBS)
 
 bin_PROGRAMS = mosh-client mosh-server
 

src/network/network.cc

@@ -16,6 +16,8 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include "config.h"
+
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
@@ -23,6 +25,14 @@
 #include <assert.h>
 #include <errno.h>
 
+#if HAVE_CLOCK_GETTIME
+ #include <time.h>
+#elif HAVE_MACH_ABSOLUTE_TIME
+ #include <mach/mach_time.h>
+#elif HAVE_GETTIMEOFDAY
+ #include <sys/time.h>
+#endif
+
 #include "dos_assert.h"
 #include "byteorder.h"
 #include "network.h"
@@ -282,6 +292,7 @@ int Connection::port( void ) const
 
 uint64_t Network::timestamp( void )
 {
+#if HAVE_CLOCK_GETTIME
   struct timespec tp;
 
   if ( clock_gettime( CLOCK_MONOTONIC, &tp ) < 0 ) {
@@ -292,6 +303,30 @@ uint64_t Network::timestamp( void )
   millis += uint64_t( tp.tv_sec ) * 1000;
 
   return millis;
+#elif HAVE_MACH_ABSOLUTE_TIME
+  static mach_timebase_info_data_t s_timebase_info;
+
+  if (s_timebase_info.denom == 0) {
+    mach_timebase_info(&s_timebase_info);
+  }
+
+  // NB: mach_absolute_time() returns "absolute time units"
+  // We need to apply a conversion to get milliseconds.
+  return ((mach_absolute_time() * s_timebase_info.numer) / (1000000 * s_timebase_info.denom));
+#elif HAVE_GETTIMEOFDAY
+  // NOTE: If time steps backwards, timeouts may be confused.
+  struct timeval tv;
+  if ( gettimeofday(&tv, NULL) ) {
+    throw NetworkException( "gettimeofday", errno );
+  }
+
+  uint64_t millis = tv.tv_usec / 1000;
+  millis += uint64_t( tv.tv_sec ) * 1000;
+
+  return millis;
+#else
+# error "Don't know how to get a timestamp on this platform"
+#endif
 }
 
 uint16_t Network::timestamp16( void )