Re: [PATCH v3] net/tls: Fix return values to avoid ENOTSUPP

On Thu, Dec 5, 2019 at 3:44 PM Valentin Vidić
[off-list ref] wrote:

On Thu, Dec 05, 2019 at 03:06:55PM -0500, Willem de Bruijn wrote:

quoted

On Thu, Dec 5, 2019 at 2:34 PM Jakub Kicinski
[off-list ref] wrote:

quoted

On Thu,  5 Dec 2019 07:41:18 +0100, Valentin Vidic wrote:

quoted

ENOTSUPP is not available in userspace, for example:

  setsockopt failed, 524, Unknown error 524

Signed-off-by: Valentin Vidic <redacted>

quoted

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index 0683788bbef0..cd91ad812291 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c

@@ -429,7 +429,7 @@ static int tls_push_data(struct sock *sk,

      if (flags &
          ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL | MSG_SENDPAGE_NOTLAST))
-             return -ENOTSUPP;
+             return -EOPNOTSUPP;

      if (unlikely(sk->sk_err))
              return -sk->sk_err;

@@ -571,7 +571,7 @@ int tls_device_sendpage(struct sock *sk, struct page *page,
      lock_sock(sk);

      if (flags & MSG_OOB) {
-             rc = -ENOTSUPP;
+             rc = -EOPNOTSUPP;

Perhaps the flag checks should return EINVAL? Willem any opinions?

No strong opinion. Judging from do_tcp_sendpages MSG_OOB is a
supported flag in general for sendpage, so signaling that the TLS
variant cannot support that otherwise valid request sounds fine to me.

I based these on the description from the sendmsg manpage, but you decide:

EOPNOTSUPP
    Some bit in the flags argument is inappropriate for the socket type.

Interesting. That is a narrower interpretation than asm-generic/errno.h

  #define EOPNOTSUPP      95      /* Operation not supported on
transport endpoint */

which is also the string that strerror() generates.

quoted

quoted

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diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index bdca31ffe6da..5830b8e02a36 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c

@@ -496,7 +496,7 @@ static int do_tls_setsockopt_conf(struct sock *sk, char __user *optval,
      /* check version */
      if (crypto_info->version != TLS_1_2_VERSION &&
          crypto_info->version != TLS_1_3_VERSION) {
-             rc = -ENOTSUPP;
+             rc = -EINVAL;

This one I think Willem asked to be EOPNOTSUPP OTOH.

Indeed (assuming no one disagrees). Based on the same rationale: the
request may be valid, it just cannot be accommodated (yet).

In this case other checks in the same function like crypto_info->cipher_type
return EINVAL, so I used the same here.

That makes sense.

I think there is a fundamental difference between, say, passing an
argument of incorrect length (optlen < sizeof(..)) and asking for a
possibly unsupported cipher mode. But consistency trumps that.

I don't mean to drag this out by bike-shedding.

Happy to defer to maintainers on whether the errno on published code
can and should be changed, which is the more fundamental issue than
the exact errno.

FWIW, I also did not see existing openssl and gnutls callers test the
specific errno. The calls just fail on any setsockopt return value -1.