Fix an additional multiple-write case noted by John, where sendauth

calls write_message twice in a row.

Add new function krb5int_write_messages, calls krb5_net_writev with
multiple messages (currently only two at a time).  Use it from
krb5_write_message and krb5_sendauth.

ticket: 6339

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@21752 dc483132-0cff-0310-8789-dd5450dbe970

1 files changed, 35 insertions, 9 deletions

diff --git a/src/lib/krb5/os/write_msg.c b/src/lib/krb5/os/write_msg.c
index 86b9275d74..7586c9b869 100644
--- a/src/lib/krb5/os/write_msg.c
+++ b/src/lib/krb5/os/write_msg.c
@@ -31,18 +31,44 @@
 #include <errno.h>
 #include "os-proto.h"
 
+/* Try to write a series of messages with as few write(v) system calls
+   as possible, to avoid Nagle/DelayedAck problems.  Cheating here a
+   little -- I know the only cases we have at the moment will send one
+   or two messages in a call.  Sending more will work, but not as
+   efficiently.  */
 krb5_error_code
-krb5_write_message(krb5_context context, krb5_pointer fdp, krb5_data *outbuf)
+krb5int_write_messages(krb5_context context, krb5_pointer fdp, krb5_data *outbuf, int nbufs)
 {
-	krb5_int32	len;
-	int		fd = *( (int *) fdp);
-	sg_buf		sg[2];
+    int fd = *( (int *) fdp);
+
+    while (nbufs) {
+	int nbufs1;
+	sg_buf sg[4];
+	krb5_int32 len[2];
 
-	len = htonl(outbuf->length);
-	SG_SET(&sg[0], &len, 4);
-	SG_SET(&sg[1], outbuf->data, outbuf->length);
-	if (krb5int_net_writev(context, fd, sg, 2) < 0) {
+	if (nbufs > 1)
+	    nbufs1 = 2;
+	else
+	    nbufs1 = 1;
+	len[0] = htonl(outbuf[0].length);
+	SG_SET(&sg[0], &len[0], 4);
+	SG_SET(&sg[1], outbuf[0].data, outbuf[0].length);
+	if (nbufs1 == 2) {
+	    len[1] = htonl(outbuf[1].length);
+	    SG_SET(&sg[2], &len[1], 4);
+	    SG_SET(&sg[3], outbuf[1].data, outbuf[1].length);
+	}
+	if (krb5int_net_writev(context, fd, sg, nbufs1 * 2) < 0) {
 	    return errno;
 	}
-	return(0);
+	outbuf += nbufs1;
+	nbufs -= nbufs1;
+    }
+    return(0);
+}
+
+krb5_error_code
+krb5_write_message(krb5_context context, krb5_pointer fdp, krb5_data *outbuf)
+{
+    return krb5int_write_messages(context, fdp, outbuf, 1);
 }