[PATCH] tap: Use single counter for iov elements in tap_send_frames_pasta()

[PATCH] tap: Use single counter for iov elements in tap_send_frames_pasta()

[Stefano Brivio]

David points out that using multiple counters to go over the iov
array, namely 'i' and 'iov', makes mistakes easier. We can't just use
'iov', unless we reserve an element with zero iov_len at the end,
which isn't really justified.

Simply use 'i' to iterate over the array.

Link: https://archives.passt.top/passt-dev/Y+mfenvLn3VJ7Dg5@yekko/
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
 tap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tap.c b/tap.c
index 02da84d..e4c5b5b 100644
--- a/tap.c
+++ b/tap.c
@@ -316,13 +316,13 @@ static void tap_send_frames_pasta(struct ctx *c,
 {
 	size_t i;
 
-	for (i = 0; i < n; i++, iov++) {
-		if (write(c->fd_tap, (char *)iov->iov_base, iov->iov_len) < 0) {
+	for (i = 0; i < n; i++) {
+		if (write(c->fd_tap, (char *)iov[i].iov_base,
+			  iov[i].iov_len) < 0) {
 			debug("tap write: %s", strerror(errno));
 			if (errno != EAGAIN && errno != EWOULDBLOCK)
 				tap_handler(c, c->fd_tap, EPOLLERR, NULL);
 			i--;
-			iov--;
 		}
 	}
 }
-- 
@@ -316,13 +316,13 @@ static void tap_send_frames_pasta(struct ctx *c,
 {
 	size_t i;
 
-	for (i = 0; i < n; i++, iov++) {
-		if (write(c->fd_tap, (char *)iov->iov_base, iov->iov_len) < 0) {
+	for (i = 0; i < n; i++) {
+		if (write(c->fd_tap, (char *)iov[i].iov_base,
+			  iov[i].iov_len) < 0) {
 			debug("tap write: %s", strerror(errno));
 			if (errno != EAGAIN && errno != EWOULDBLOCK)
 				tap_handler(c, c->fd_tap, EPOLLERR, NULL);
 			i--;
-			iov--;
 		}
 	}
 }
-- 
2.35.1

Re: [PATCH] tap: Use single counter for iov elements in tap_send_frames_pasta()

[David Gibson]

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On Thu, Feb 16, 2023 at 02:08:19AM +0100, Stefano Brivio wrote:
> David points out that using multiple counters to go over the iov
> array, namely 'i' and 'iov', makes mistakes easier. We can't just use
> 'iov', unless we reserve an element with zero iov_len at the end,
> which isn't really justified.
> 
> Simply use 'i' to iterate over the array.
> 
> Link: https://archives.passt.top/passt-dev/Y+mfenvLn3VJ7Dg5@yekko/
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  tap.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tap.c b/tap.c
> index 02da84d..e4c5b5b 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -316,13 +316,13 @@ static void tap_send_frames_pasta(struct ctx *c,
>  {
>  	size_t i;
>  
> -	for (i = 0; i < n; i++, iov++) {
> -		if (write(c->fd_tap, (char *)iov->iov_base, iov->iov_len) < 0) {
> +	for (i = 0; i < n; i++) {
> +		if (write(c->fd_tap, (char *)iov[i].iov_base,
> +			  iov[i].iov_len) < 0) {
>  			debug("tap write: %s", strerror(errno));
>  			if (errno != EAGAIN && errno != EWOULDBLOCK)
>  				tap_handler(c, c->fd_tap, EPOLLERR, NULL);
>  			i--;
> -			iov--;
>  		}
>  	}
>  }

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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