On 2022-01-25 09:06, John Fastabend wrote:

Maxim Mikityanskiy wrote:

quoted

When CONFIG_SYN_COOKIES is off, bpf_tcp_check_syncookie returns
ENOTSUPP. It's a non-standard and deprecated code. The related function
bpf_tcp_gen_syncookie and most of the other functions use EOPNOTSUPP if
some feature is not available. This patch changes ENOTSUPP to EOPNOTSUPP
in bpf_tcp_check_syncookie.

Fixes: 399040847084 ("bpf: add helper to check for a valid SYN cookie")
Signed-off-by: Maxim Mikityanskiy <redacted>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>

This came up in another thread? Or was it the same and we lost the context
in the commit msg. Either way I don't think we should start one-off
changing these user facing error codes. Its not the only spot we do this
and its been this way for sometime.

Is it causing a real problem?

I'm not aware of anyone complaining about it. It's just a cleanup to use 
the proper error code, since ENOTSUPP is a non-standard one (used in 
NFS?), for example, strerror() returns "Unknown error 524" instead of 
"Operation not supported".

Source: Documentation/dev-tools/checkpatch.rst:

 > ENOTSUPP is not a standard error code and should be avoided in new
 > patches. EOPNOTSUPP should be used instead.
 >
 > See: https://lore.kernel.org/netdev/20200510182252.GA411829@lunn.ch/ (local)

quoted

---
  net/core/filter.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 780e635fb52a..2c9106704821 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c

@@ -6814,7 +6814,7 @@ BPF_CALL_5(bpf_tcp_check_syncookie, struct sock *, sk, void *, iph, u32, iph_len
  
  	return -ENOENT;
  #else
-	return -ENOTSUPP;
+	return -EOPNOTSUPP;
  #endif
  }
  

-- 
2.30.2