Consolidate raw socket acquisition.

libnetutil/netutil.cc

@@ -1088,6 +1088,98 @@ void eth_close_cached() {
   return;
 }
 
+static void netutil_perror(const char *msg) {
+  int err = socket_errno();
+  netutil_error("%s: (%d) %s", msg, err, socket_strerror(err));
+}
+
+/* Create a raw socket and do things that always apply to raw sockets:
+    * Set SO_BROADCAST.
+    * Set IP_HDRINCL.
+    * Bind to an interface with SO_BINDTODEVICE (if device is not NULL).
+   The socket is created with address family AF_INET, but may be usable for
+   AF_INET6, depending on the operating system. */
+int netutil_raw_socket(const char *device) {
+#ifdef WIN32
+  netutil_error("Windows does not have adequate raw socket support.");
+  return -1;
+#else
+  int rawsd;
+  int one = 1;
+
+  rawsd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
+  if (rawsd < 0) {
+    netutil_perror("Couldn't open a raw socket. "
+#if defined(sun) && defined(__SVR4)
+        "In Solaris shared-IP non-global zones, this requires the PRIV_NET_RAWACCESS privilege. "
+#endif
+        "Error");
+    return -1;
+  }
+  if (setsockopt (rawsd, SOL_SOCKET, SO_BROADCAST, (const char *) &one, sizeof(int)) != 0) {
+    netutil_perror("setsockopt(SO_BROADCAST) failed");
+  }
+  sethdrinclude(rawsd);
+  socket_bindtodevice(rawsd, device);
+
+  return rawsd;
+#endif
+}
+
+int raw_socket_or_eth(int sendpref, const char *ifname,
+    int *rawsd, netutil_eth_t **ethsd) {
+  assert(rawsd != NULL);
+  *rawsd = -1;
+  assert(ethsd != NULL);
+  *ethsd = NULL;
+  bool may_try_eth = ifname && !(sendpref & PACKET_SEND_IP_STRONG);
+  bool may_try_ip = !(sendpref & PACKET_SEND_ETH_STRONG);
+  bool try_eth = may_try_eth && (sendpref & PACKET_SEND_ETH);
+  bool try_ip = may_try_ip && (sendpref & PACKET_SEND_IP);
+
+  for (int i = 0; i < 2; i++) {
+    if (try_eth) {
+      try_eth = false;
+      may_try_eth = false;
+      try_ip = may_try_ip;
+
+      netutil_eth_t *e = eth_open_cached(ifname);
+      *ethsd = e;
+      if (e == NULL) {
+        netutil_error("dnet: failed to open device %s", ifname);
+      }
+      else if (!netutil_eth_can_send(e)) {
+        netutil_error("%s is not a supported device for sending.", ifname);
+        e = NULL;
+      }
+      else {
+        break;
+      }
+    }
+
+    if (try_ip) {
+      try_ip = false;
+      may_try_ip = false;
+      try_eth = may_try_eth;
+
+#ifdef WIN32
+      /* For Windows, don't even bother trying unless the caller insists, to
+       * avoid excessive error messages. */
+      if (!(sendpref & PACKET_SEND_IP_STRONG)) {
+        continue;
+      }
+#endif
+      int sd = netutil_raw_socket(ifname);
+      *rawsd = sd;
+      if (sd >= 0) {
+        break;
+      }
+    }
+  }
+
+  return (*ethsd != NULL || *rawsd >= 0) ? 1 : 0;
+}
+
 /* Takes a protocol number like IPPROTO_TCP, IPPROTO_UDP, IPPROTO_IP,
  * etc, and returns an ASCII representation (or the string "unknown" if
  * it doesn't recognize the number). If uppercase is non zero, the