Call pcap_set_immediate_mode to get results back immediately.

CHANGELOG

@@ -1,5 +1,10 @@
 #Nmap Changelog ($Id$); -*-text-*-
 
+o [GH#1291][GH#34] Use pcap_create instead of pcap_live_open in Nmap, and set
+  immediate mode on the pcap descriptor. This solves packet loss problems on
+  Linux and may improve performance on other platforms. [Daniel Cater, Mike
+  Pontillo, Daniel Miller]
+
 o [GH#1150] Start host timeout clocks when the first probe is sent to a host,
   not when the hostgroup is started. Sometimes a host doesn't get probes until
   late in the hostgroup, increasing the chance it will time out. [jsiembida]

configure

@@ -1948,48 +1948,6 @@ $as_echo "$ac_res" >&6; }
 
 } # ac_fn_c_check_decl
 
-# ac_fn_cxx_try_run LINENO
-# ------------------------
-# Try to link conftest.$ac_ext, and return whether this succeeded. Assumes
-# that executables *can* be run.
-ac_fn_cxx_try_run ()
-{
-  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
-  if { { ac_try="$ac_link"
-case "(($ac_try" in
-  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
-  *) ac_try_echo=$ac_try;;
-esac
-eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
-  (eval "$ac_link") 2>&5
-  ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; } && { ac_try='./conftest$ac_exeext'
-  { { case "(($ac_try" in
-  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
-  *) ac_try_echo=$ac_try;;
-esac
-eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
-$as_echo "$ac_try_echo"; } >&5
-  (eval "$ac_try") 2>&5
-  ac_status=$?
-  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
-  test $ac_status = 0; }; }; then :
-  ac_retval=0
-else
-  $as_echo "$as_me: program exited with status $ac_status" >&5
-       $as_echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-       ac_retval=$ac_status
-fi
-  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
-  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
-  as_fn_set_status $ac_retval
-
-} # ac_fn_cxx_try_run
-
 # ac_fn_c_check_func LINENO FUNC VAR
 # ----------------------------------
 # Tests whether FUNC exists, setting the cache variable VAR accordingly
@@ -2056,6 +2014,48 @@ $as_echo "$ac_res" >&6; }
   eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
 
 } # ac_fn_c_check_func
+
+# ac_fn_cxx_try_run LINENO
+# ------------------------
+# Try to link conftest.$ac_ext, and return whether this succeeded. Assumes
+# that executables *can* be run.
+ac_fn_cxx_try_run ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  if { { ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+$as_echo "$ac_try_echo"; } >&5
+  (eval "$ac_link") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; } && { ac_try='./conftest$ac_exeext'
+  { { case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+$as_echo "$ac_try_echo"; } >&5
+  (eval "$ac_try") 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }; then :
+  ac_retval=0
+else
+  $as_echo "$as_me: program exited with status $ac_status" >&5
+       $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+       ac_retval=$ac_status
+fi
+  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+  as_fn_set_status $ac_retval
+
+} # ac_fn_cxx_try_run
 cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
@@ -6413,6 +6413,9 @@ if test $have_libpcap != yes; then
 
 $as_echo "#define PCAP_INCLUDED 1" >>confdefs.h
 
+
+$as_echo "#define HAVE_PCAP_SET_IMMEDIATE_MODE 1" >>confdefs.h
+
 else
   # We assume our included libpcap doesn't need this check-and-define
 
@@ -6452,6 +6455,17 @@ $as_echo "#define PCAP_NETMASK_UNKNOWN 0" >>confdefs.h
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_have_pcap_netmask_unknown" >&5
 $as_echo "$ac_cv_have_pcap_netmask_unknown" >&6; }
 
+  for ac_func in pcap_set_immediate_mode
+do :
+  ac_fn_c_check_func "$LINENO" "pcap_set_immediate_mode" "ac_cv_func_pcap_set_immediate_mode"
+if test "x$ac_cv_func_pcap_set_immediate_mode" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_PCAP_SET_IMMEDIATE_MODE 1
+_ACEOF
+
+fi
+done
+
 
 
 $as_echo "#define HAVE_LIBPCAP 1" >>confdefs.h

configure.ac

@@ -479,9 +479,11 @@ if test $have_libpcap != yes; then
   PCAP_CLEAN="clean-pcap"
   PCAP_DIST_CLEAN="distclean-pcap"
   AC_DEFINE(PCAP_INCLUDED, 1, [Using included libpcap])
+  AC_DEFINE(HAVE_PCAP_SET_IMMEDIATE_MODE, 1, [Included libpcap has pcap_set_immediate_mode])
 else
   # We assume our included libpcap doesn't need this check-and-define
   PCAP_DEFINE_NETMASK_UNKNOWN
+  AC_CHECK_FUNCS([pcap_set_immediate_mode])
 
   AC_DEFINE(HAVE_LIBPCAP, 1, [Have libpcap library])
   LIBPCAP_LIBS="-lpcap"

libnetutil/netutil.cc

@@ -4127,6 +4127,9 @@ pcap_t *my_pcap_open_live(const char *device, int snaplen, int promisc, int to_m
   MY_PCAP_SET(pcap_set_snaplen, pt, snaplen);
   MY_PCAP_SET(pcap_set_promisc, pt, promisc);
   MY_PCAP_SET(pcap_set_timeout, pt, to_ms);
+#ifdef HAVE_PCAP_SET_IMMEDIATE_MODE
+  MY_PCAP_SET(pcap_set_immediate_mode, pt, 1);
+#endif
 
   failed = pcap_activate(pt);
   if (failed < 0) {
@@ -4147,6 +4150,9 @@ pcap_t *my_pcap_open_live(const char *device, int snaplen, int promisc, int to_m
   }
   CloseHandle(pcapMutex);
   /* We want any responses back ASAP */
+  /* This is unnecessary with Npcap since libpcap calls PacketSetMinToCopy(0)
+   * based on immediate mode. Have not determined if it is needed for WinPcap
+   * or not, but it's not hurting anything. */
   pcap_setmintocopy(pt, 1);
 #endif
 

nmap_config.h.in

@@ -255,5 +255,6 @@ extern "C" int gethostname (char *, unsigned int);
 
 #undef HAVE_IPV6_IPPROTO_RAW
 #undef PCAP_NETMASK_UNKNOWN
+#undef HAVE_PCAP_SET_IMMEDIATE_MODE
 
 #endif /* CONFIG_H */