[PATCH v7] 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.

Fixes: fb4ee67529ff ("net/ncsi: Add NCSI OEM command support")
Signed-off-by: Kumar Thangavel <redacted>
Acked-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Reviewed-by: Paul Menzel <redacted>

---
  v7:
   - Updated padding_bytes as const static int variable

  v6:
   - Updated type of padding_bytes variable
   - Updated type of payload
   - Seperated variable declarations and code

  v5:
   - Added Fixes tag
   - Added const variable for padding_bytes

  v4:
   - Used 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 | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/net/ncsi/ncsi-cmd.c b/net/ncsi/ncsi-cmd.c
index ba9ae482141b..9a6f10f4833e 100644
--- a/net/ncsi/ncsi-cmd.c
+++ b/net/ncsi/ncsi-cmd.c

@@ -18,6 +18,8 @@
 #include "internal.h"
 #include "ncsi-pkt.h"
 
+const static int padding_bytes = 26;
+
 u32 ncsi_calculate_checksum(unsigned char *data, int len)
 {
 	u32 checksum = 0;

@@ -213,12 +215,17 @@ static int ncsi_cmd_handler_oem(struct sk_buff *skb,
 {
 	struct ncsi_cmd_oem_pkt *cmd;
 	unsigned int len;
+	int payload;
+	/* 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
+	 */
 
+	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, padding_bytes);
 
 	cmd = skb_put_zero(skb, len);
 	memcpy(&cmd->mfr_id, nca->data, nca->payload);

@@ -272,6 +279,7 @@ 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 +289,14 @@ 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, padding_bytes);
 
 	/* Allocate skb */
 	skb = alloc_skb(len, GFP_ATOMIC);

-- 
2.17.1

On 11/18/21 8:03 AM, Kumar Thangavel wrote:

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.

Patch title should start with a prefix, identifying which layer/driver is
involved.

Probably in this case

net/ncsi: Add payload to be 32-bit aligned to fix dropped packets

It would be nice to have some kind of reference, to explain
what is this magic value.

Moving the comment [1] here might make sense.

[1] This comment could be moved before @padding_bytes

Hi Kumar,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.16-rc1 next-20211118]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Kumar-Thangavel/Add-payload-to-be-32-bit-aligned-to-fix-dropped-packets/20211119-000541
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 42eb8fdac2fc5d62392dcfcf0253753e821a97b0
config: m68k-randconfig-r005-20211118 (attached as .config)
compiler: m68k-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/f4e0a51f25ba398ad7f2e3efa5076b2e0ad24e3b
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Kumar-Thangavel/Add-payload-to-be-32-bit-aligned-to-fix-dropped-packets/20211119-000541
        git checkout f4e0a51f25ba398ad7f2e3efa5076b2e0ad24e3b
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=m68k 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All warnings (new ones prefixed by >>):

quoted

net/ncsi/ncsi-cmd.c:21:1: warning: 'static' is not at beginning of declaration [-Wold-style-declaration]

      21 | const static int padding_bytes = 26;
         | ^~~~~


vim +/static +21 net/ncsi/ncsi-cmd.c

    20	
  > 21	const static int padding_bytes = 26;
    22	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

On Thu, 18 Nov 2021 21:33:02 +0530 Kumar Thangavel wrote:

+const static int padding_bytes = 26;

/net/ncsi/ncsi-cmd.c:21:1: warning: ‘static’ is not at beginning of declaration [-Wold-style-declaration]
   21 | const static int padding_bytes = 26;
      | ^~~~~