netdev - [PATCH net-next 07/10] tls: rx: replace 'back' with 'offset'

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Date:   Thu,  7 Apr 2022 20:38:20 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     davem@...emloft.net, pabeni@...hat.com
Cc:     netdev@...r.kernel.org, borisp@...dia.com,
        john.fastabend@...il.com, daniel@...earbox.net,
        vfedorenko@...ek.ru, Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next 07/10] tls: rx: replace 'back' with 'offset'

The padding length TLS 1.3 logic is searching for content_type from
the end of text. IMHO the code is easier to parse if we calculate
offset and decrement it rather than try to maintain positive offset
from the end of the record called "back".

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
 net/tls/tls_sw.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 579ccfd011a1..9729244ce3fc 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -136,22 +136,21 @@ static int padding_length(struct tls_prot_info *prot, struct sk_buff *skb)
 
 	/* Determine zero-padding length */
 	if (prot->version == TLS_1_3_VERSION) {
-		int back = TLS_TAG_SIZE + 1;
+		int offset = rxm->full_len - TLS_TAG_SIZE - 1;
 		char content_type = 0;
 		int err;
 
 		while (content_type == 0) {
-			if (back > rxm->full_len - prot->prepend_size)
+			if (offset < prot->prepend_size)
 				return -EBADMSG;
-			err = skb_copy_bits(skb,
-					    rxm->offset + rxm->full_len - back,
+			err = skb_copy_bits(skb, rxm->offset + offset,
 					    &content_type, 1);
 			if (err)
 				return err;
 			if (content_type)
 				break;
 			sub++;
-			back++;
+			offset--;
 		}
 		tlm->control = content_type;
 	}
-- 
2.34.1