Re: uapi header mismatch with kernel ?

[Daniel Borkmann <dborkman@redhat.com>]

On 08/28/2014 08:33 AM, 苏庆 wrote:
> Hi all,
>
> I found that In 3.x kernel, the sctp states are defined differently
> between kernel and uapi header. This makes our application fails to
> work.
>
> Is that a mismatch or am I missing something?

You are correct, and that's not good ... can you try out the below
kernel patch?

 From 90653829a4d406898f6906849f3eca481ec01894 Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman@redhat.com>
Date: Thu, 28 Aug 2014 09:26:36 +0200
Subject: [PATCH] net: sctp: fix ABI through sctp_assoc_to_state helper

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
---
  include/net/sctp/sctp.h | 13 +++++++++++++
  net/sctp/socket.c       |  2 +-
  2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index f6e7397..f50dccf 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -320,6 +320,19 @@ static inline sctp_assoc_t sctp_assoc2id(const struct sctp_association *asoc)
  	return asoc ? asoc->assoc_id : 0;
  }

+static inline enum sctp_sstat_state
+sctp_assoc_to_state(const struct sctp_association *asoc)
+{
+	/* SCTP's uapi always had SCTP_EMPTY(=0) as a dummy state, but we
+	 * got rid of it in kernel space. Therefore SCTP_CLOSED et al
+	 * start at =1 in user space, but actually as =0 in kernel space.
+	 * Now that we may not break user space and SCTP_EMPTY is exposed
+	 * there, hence we need to fix it up with an ugly offset to not
+	 * break applications. :(
+	 */
+	return asoc->state + 1;
+}
+
  /* Look up the association by its id.  */
  struct sctp_association *sctp_id2assoc(struct sock *sk, sctp_assoc_t id);

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index eb71d49..634a2ab 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4243,7 +4243,7 @@ static int sctp_getsockopt_sctp_status(struct sock *sk, int len,
  	transport = asoc->peer.primary_path;

  	status.sstat_assoc_id = sctp_assoc2id(asoc);
-	status.sstat_state = asoc->state;
+	status.sstat_state = sctp_assoc_to_state(asoc);
  	status.sstat_rwnd =  asoc->peer.rwnd;
  	status.sstat_unackdata = asoc->unack_data;

-- 
1.7.11.7