Index: sys/netinet/netdump/netdump.h
===================================================================
--- sys/netinet/netdump/netdump.h
+++ sys/netinet/netdump/netdump.h
@@ -78,6 +78,11 @@
 
 #define	NETDUMP_MAX_IN_FLIGHT	64
 
+struct nd_ctx {
+	off_t nd_tx_off;
+	size_t nd_buf_len;
+};
+
 enum netdump_ev {
 	NETDUMP_START,
 	NETDUMP_END,
Index: sys/netinet/netdump/netdump_client.c
===================================================================
--- sys/netinet/netdump/netdump_client.c
+++ sys/netinet/netdump/netdump_client.c
@@ -935,7 +935,7 @@
  *	errno on error
  */
 static int
-netdump_dumper(void *priv __unused, void *virtual,
+netdump_dumper(void *priv, void *virtual,
     vm_offset_t physical __unused, off_t offset, size_t length)
 {
 	int error;
@@ -943,7 +943,15 @@
 	NETDDEBUGV("netdump_dumper(NULL, %p, NULL, %ju, %zu)\n",
 	    virtual, (uintmax_t)offset, length);
 
+	struct nd_ctx *ctx = (struct nd_ctx*)priv;
+
 	if (virtual == NULL) {
+		if (ctx->nd_buf_len != 0) {
+			error = netdump_send(NETDUMP_VMCORE, ctx->nd_tx_off, nd_buf, 
+					ctx->nd_buf_len);
+			if (error != 0)
+				dump_failed = 1;
+		}
 		if (dump_failed != 0)
 			printf("failed to dump the kernel core\n");
 		else if (netdump_send(NETDUMP_FINISHED, 0, NULL, 0) != 0)
@@ -956,12 +964,20 @@
 	if (length > sizeof(nd_buf))
 		return (ENOSPC);
 
-	memmove(nd_buf, virtual, length);
-	error = netdump_send(NETDUMP_VMCORE, offset, nd_buf, length);
-	if (error != 0) {
-		dump_failed = 1;
-		return (error);
+	if (ctx->nd_buf_len + length > sizeof(nd_buf)) {
+		error = netdump_send(NETDUMP_VMCORE, ctx->nd_tx_off, nd_buf, 
+				ctx->nd_buf_len);
+		if (error != 0) {
+			dump_failed = 1;
+			return (error);
+		}
+		ctx->nd_buf_len = 0;
+		ctx->nd_tx_off = offset;
 	}
+
+	memmove(nd_buf + ctx->nd_buf_len, virtual, length);
+	ctx->nd_buf_len += length;
+
 	return (0);
 }
 
@@ -1232,6 +1248,7 @@
 {
 	struct diocskerneldump_arg kda_copy, *conf;
 	struct dumperinfo dumper;
+	struct nd_ctx *nd_tx_state;
 	uint8_t *encryptedkey;
 	int error;
 #ifdef COMPAT_FREEBSD11
@@ -1397,11 +1414,14 @@
 			conf->kda_encryptedkey = encryptedkey;
 		}
 
+		nd_tx_state = malloc(sizeof(struct nd_ctx), M_TEMP, M_WAITOK);
+		memset(nd_tx_state, 0, sizeof(struct nd_ctx));
+
 		memset(&dumper, 0, sizeof(dumper));
 		dumper.dumper_start = netdump_start;
 		dumper.dumper_hdr = netdump_write_headers;
 		dumper.dumper = netdump_dumper;
-		dumper.priv = NULL;
+		dumper.priv = nd_tx_state;
 		dumper.blocksize = NETDUMP_DATASIZE;
 		dumper.maxiosize = MAXDUMPPGS * PAGE_SIZE;
 		dumper.mediaoffset = 0;