* [libnftnl PATCH 2/2] src: improve printing of XML/JSON event wrapper header/footer
2014-08-25 13:02 [libnftnl PATCH 1/2] utils: ensure \0 is in place in nft_fprintf() Arturo Borrero Gonzalez
@ 2014-08-25 13:02 ` Arturo Borrero Gonzalez
2014-08-25 14:12 ` Pablo Neira Ayuso
2014-08-25 14:09 ` [libnftnl PATCH 1/2] utils: ensure \0 is in place in nft_fprintf() Pablo Neira Ayuso
1 sibling, 1 reply; 4+ messages in thread
From: Arturo Borrero Gonzalez @ 2014-08-25 13:02 UTC (permalink / raw)
To: netfilter-devel; +Cc: pablo
Use the nft_fprintf() helper. The helper handles \0 properly.
Before this patch, we get trash in the output due to the buffer being printed
without any \0.
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
---
src/common.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)
diff --git a/src/common.c b/src/common.c
index 3ceb811..a6f2508 100644
--- a/src/common.c
+++ b/src/common.c
@@ -114,14 +114,15 @@ int nft_event_header_snprintf(char *buf, size_t size, uint32_t type,
return ret;
}
-int nft_event_header_fprintf(FILE *fp, uint32_t type, uint32_t flags)
+static int nft_event_header_fprintf_cb(char *buf, size_t size, void *unused,
+ uint32_t type, uint32_t flags)
{
- char buf[64]; /* enough for the maximum string length above */
-
- nft_event_header_snprintf(buf, sizeof(buf), type, flags);
- buf[sizeof(buf) - 1] = '\0';
+ return nft_event_header_snprintf(buf, size, type, flags);
+}
- return fprintf(fp, "%s", buf);
+int nft_event_header_fprintf(FILE *fp, uint32_t type, uint32_t flags)
+{
+ return nft_fprintf(fp, NULL, type, flags, nft_event_header_fprintf_cb);
}
int nft_event_footer_snprintf(char *buf, size_t size, uint32_t type,
@@ -140,6 +141,17 @@ int nft_event_footer_snprintf(char *buf, size_t size, uint32_t type,
}
}
+static int nft_event_footer_fprintf_cb(char *buf, size_t size, void *unused,
+ uint32_t type, uint32_t flags)
+{
+ return nft_event_footer_snprintf(buf, size, type, flags);
+}
+
+int nft_event_footer_fprintf(FILE *fp, uint32_t type, uint32_t flags)
+{
+ return nft_fprintf(fp, NULL, type, flags, nft_event_footer_fprintf_cb);
+}
+
static void nft_batch_build_hdr(char *buf, uint16_t type, uint32_t seq)
{
struct nlmsghdr *nlh;
@@ -168,16 +180,6 @@ void nft_batch_end(char *buf, uint32_t seq)
}
EXPORT_SYMBOL(nft_batch_end);
-int nft_event_footer_fprintf(FILE *fp, uint32_t type, uint32_t flags)
-{
- char buf[32]; /* enough for the maximum string length above */
-
- nft_event_footer_snprintf(buf, sizeof(buf), type, flags);
- buf[sizeof(buf) - 1] = '\0';
-
- return fprintf(fp, "%s", buf);
-}
-
int nft_batch_is_supported(void)
{
struct mnl_socket *nl;
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [libnftnl PATCH 1/2] utils: ensure \0 is in place in nft_fprintf()
2014-08-25 13:02 [libnftnl PATCH 1/2] utils: ensure \0 is in place in nft_fprintf() Arturo Borrero Gonzalez
2014-08-25 13:02 ` [libnftnl PATCH 2/2] src: improve printing of XML/JSON event wrapper header/footer Arturo Borrero Gonzalez
@ 2014-08-25 14:09 ` Pablo Neira Ayuso
1 sibling, 0 replies; 4+ messages in thread
From: Pablo Neira Ayuso @ 2014-08-25 14:09 UTC (permalink / raw)
To: Arturo Borrero Gonzalez; +Cc: netfilter-devel
On Mon, Aug 25, 2014 at 03:02:21PM +0200, Arturo Borrero Gonzalez wrote:
> We must make sure the buffer contains a \0 in the last position,
> to avoid printing trash by the last fprintf() call.
snprintf already guarantees that the string is nul-terminated if there
is enough room to add \0.
ret = snprintf_cb(buf, bufsiz, obj, type, flags);
if (ret < 0)
goto out;
if (ret >= NFT_SNPRINTF_BUFSIZ) {
bufsiz = ret + 1;
buf = malloc(bufsiz);
if (buf == NULL)
return -1;
ret = snprintf_cb(buf, bufsiz, obj, type, flags);
if (ret < 0)
goto out;
}
ret = fprintf(fp, "%s", buf);
I think we have guarantees that buf is always nul-terminated after the
second try.
Patch 2/2 looks good to enough to me since it already resolves the
printed "garbage" at the end of the output issue.
^ permalink raw reply [flat|nested] 4+ messages in thread