netdev - [PATCH v4] Add payload to be 32-bit aligned to fix dropped packets

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Message-ID: <20211110095432.GA9571@gmail.com>
Date:   Wed, 10 Nov 2021 15:24:32 +0530
From:   Kumar Thangavel <kumarthangavel.hcl@...il.com>
To:     Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     openbmc@...ts.ozlabs.org, linux-aspeed@...ts.ozlabs.org,
        patrickw3@...com, Amithash Prasad <amithash@...com>,
        velumanit@....com, sdasari@...com, netdev@...r.kernel.org
Subject: [PATCH v4] Add payload to be 32-bit aligned to fix dropped packets

Update NC-SI command handler (both standard and OEM) to take into
account of payload paddings in allocating skb (in case of payload
size is not 32-bit aligned).

The checksum field follows payload field, without taking payload
padding into account can cause checksum being truncated, leading to
dropped packets.

Signed-off-by: Kumar Thangavel <thangavel.k@....com>
Acked-by: Samuel Mendoza-Jonas <sam@...dozajonas.com>
Reviewed-by: Paul Menzel <pmenzel@...gen.mpg.de>

---
  v4:
   - Updated existing macro for max function

  v3:
   - Added Macro for MAX
   - Fixed the missed semicolon

  v2:
   - Added NC-SI spec version and section
   - Removed blank line
   - corrected spellings

  v1:
   - Initial draft

---
---
 net/ncsi/ncsi-cmd.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/net/ncsi/ncsi-cmd.c b/net/ncsi/ncsi-cmd.c
index ba9ae482141b..e44fe138c20f 100644
--- a/net/ncsi/ncsi-cmd.c
+++ b/net/ncsi/ncsi-cmd.c
@@ -213,12 +213,16 @@ static int ncsi_cmd_handler_oem(struct sk_buff *skb,
 {
 	struct ncsi_cmd_oem_pkt *cmd;
 	unsigned int len;
+	/* NC-SI spec DSP_0222_1.2.0, section 8.2.2.2
+	 * requires payload to be padded with 0 to
+	 * 32-bit boundary before the checksum field.
+	 * Ensure the padding bytes are accounted for in
+	 * skb allocation
+	 */
 
+	unsigned short payload = ALIGN(nca->payload, 4);
 	len = sizeof(struct ncsi_cmd_pkt_hdr) + 4;
-	if (nca->payload < 26)
-		len += 26;
-	else
-		len += nca->payload;
+	len += max(payload, 26);
 
 	cmd = skb_put_zero(skb, len);
 	memcpy(&cmd->mfr_id, nca->data, nca->payload);
@@ -272,6 +276,7 @@ static struct ncsi_request *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
 	struct net_device *dev = nd->dev;
 	int hlen = LL_RESERVED_SPACE(dev);
 	int tlen = dev->needed_tailroom;
+	int payload;
 	int len = hlen + tlen;
 	struct sk_buff *skb;
 	struct ncsi_request *nr;
@@ -281,14 +286,14 @@ static struct ncsi_request *ncsi_alloc_command(struct ncsi_cmd_arg *nca)
 		return NULL;
 
 	/* NCSI command packet has 16-bytes header, payload, 4 bytes checksum.
+	 * Payload needs padding so that the checksum field following payload is
+	 * aligned to 32-bit boundary.
 	 * The packet needs padding if its payload is less than 26 bytes to
 	 * meet 64 bytes minimal ethernet frame length.
 	 */
 	len += sizeof(struct ncsi_cmd_pkt_hdr) + 4;
-	if (nca->payload < 26)
-		len += 26;
-	else
-		len += nca->payload;
+	payload = ALIGN(nca->payload, 4);
+	len += max(payload, 26);
 
 	/* Allocate skb */
 	skb = alloc_skb(len, GFP_ATOMIC);
-- 
2.17.1