В Fri, 16 Sep 2011 18:06:15 +0300 Roman Yeryomin <leroi.li...@gmail.com> пишет:
> On 16 September 2011 17:51, Alexander Gordeev <lasa...@lvk.cs.msu.su> wrote: > > В Fri, 16 Sep 2011 17:41:37 +0300 > > Roman Yeryomin <leroi.li...@gmail.com> пишет: > > > >> On 16 September 2011 01:40, Alexander Gordeev <lasa...@lvk.cs.msu.su> > >> wrote: > >> > В Fri, 26 Aug 2011 04:30:43 +0300 > >> > Roman Yeryomin <leroi.li...@gmail.com> пишет: > >> > > >> >> This method is much more stable than reading dd's output via stdin. > >> > > >> > What kind of problems do you have with piping dd's output to stdin? > >> > > >> > >> It outputs garbage very frequently and maccalc fails to convert the > >> mac (and as a consequence uci-default script fails to set the real mac > >> address). Try dd without piping to maccalc and you'll see. > >> I've noticed this bug on ramips platform and can't say anything about > >> other boards. > > > > Well, then this is probably a bug in dd? Or uClibc? Or kernel? > > Ok, I'll try to reproduce it. Can you please tell me what exactly is > > happening? > > > > Two different reads: > root@OpenWrt:/# dd bs=1 skip=262148 count=6 if=/dev/mtd0 > "u�������6+0 records in > 6+0 records out > root@OpenWrt:/# dd bs=1 skip=262148 count=6 if=/dev/mtd0 > "u���6+0 records in > 6+0 records out > > I don't think this is the bug in dd/kernel/uclibc - it would probably > expose when writing to a file too. > Maybe it's something with busybox. I'm not sure of cause. The bug is in maccalc. It does a single read() and expects to get everything in one shot which doesn't happen sometimes. The patch is attached. It fixes the problem according to my tests. I don't know whether Roman's change is necessary anymore. What do you think, Roman? -- Alexander
From ae35ee0ce9fc9b6cb5d8bea0a5a059df71602eab Mon Sep 17 00:00:00 2001
From: Alexander Gordeev <lasa...@lvk.cs.msu.su>
Date: Sun, 18 Sep 2011 21:43:12 +0400
Subject: [PATCH] maccalc: don't expect to get all data in one read
Signed-off-by: Alexander Gordeev <lasa...@lvk.cs.msu.su>
---
package/maccalc/src/main.c | 31 ++++++++++++++++++++++++++++++-
1 files changed, 30 insertions(+), 1 deletions(-)
diff --git a/package/maccalc/src/main.c b/package/maccalc/src/main.c
index e1e12cd..dcb5f55 100644
--- a/package/maccalc/src/main.c
+++ b/package/maccalc/src/main.c
@@ -9,6 +9,7 @@
*
*/
+#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
@@ -124,6 +125,34 @@ static int maccalc_do_mac2bin(int argc, const char *argv[])
return 0;
}
+static ssize_t read_safe(int fd, void *buf, size_t count)
+{
+ ssize_t total = 0;
+ ssize_t r;
+
+ while(count > 0) {
+ r = read(fd, buf, count);
+ if (r == 0)
+ /* EOF */
+ break;
+ if (r < 0) {
+ if (errno == EINTR)
+ /* interrupted by a signal, restart */
+ continue;
+ /* error */
+ total = -1;
+ break;
+ }
+
+ /* ok */
+ total += r;
+ count -= r;
+ buf += r;
+ }
+
+ return total;
+}
+
static int maccalc_do_bin2mac(int argc, const char *argv[])
{
unsigned char mac[MAC_ADDRESS_LEN];
@@ -134,7 +163,7 @@ static int maccalc_do_bin2mac(int argc, const char *argv[])
return ERR_INVALID;
}
- c = read(STDIN_FILENO, mac, sizeof(mac));
+ c = read_safe(STDIN_FILENO, mac, sizeof(mac));
if (c != sizeof(mac)) {
fprintf(stderr, "failed to read from stdin\n");
return ERR_IO;
--
1.7.5.4
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