dccp: Query supported CCIDs

This provides a data structure to record which CCIDs are locally supported
and three accessor functions:
 - a test function for internal use which is used to validate CCID requests
   made by the user;
 - a copy function so that the list can be used for feature-negotiation;
 - documented getsockopt() support so that the user can query capabilities.

The data structure is a table which is filled in at compile-time with the
list of available CCIDs (which in turn depends on the Kconfig choices).

Using the copy function for cloning the list of supported CCIDs is useful for
feature negotiation, since the negotiation is now with the full list of available
CCIDs (e.g. {2, 3}) instead of the default value {2}. This means negotiation
will not fail if the peer requests to use CCID3 instead of CCID2.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>

diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index 39131a3c78f8826bb9949ddf25ff50e591904028..f0aeb20fa63bb9aff3766cc1aca59ea0991723a0 100644 (file)
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -57,6 +57,10 @@ can be set before calling bind().
 DCCP_SOCKOPT_GET_CUR_MPS is read-only and retrieves the current maximum packet
 size (application payload size) in bytes, see RFC 4340, section 14.
 
+DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs
+supported by the endpoint (see include/linux/dccp.h for symbolic constants).
+The caller needs to provide a sufficiently large (> 2) array of type uint8_t.
+
 DCCP_SOCKOPT_SERVER_TIMEWAIT enables the server (listening socket) to hold
 timewait state when closing the connection (RFC 4340, 8.3). The usual case is
 that the closing server sends a CloseReq, whereupon the client holds timewait

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index 484b8a1fb023ac303ecbc209e9c3228498436f9c..d3ac1bde60b4cbf09e090c3d67048abae7bf8fa1 100644 (file)
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -209,6 +209,7 @@ struct dccp_so_feat {
 #define DCCP_SOCKOPT_SERVER_TIMEWAIT   6
 #define DCCP_SOCKOPT_SEND_CSCOV                10
 #define DCCP_SOCKOPT_RECV_CSCOV                11
+#define DCCP_SOCKOPT_AVAILABLE_CCIDS   12
 #define DCCP_SOCKOPT_CCID_RX_INFO      128
 #define DCCP_SOCKOPT_CCID_TX_INFO      192
 

diff --git a/net/dccp/ccid.c b/net/dccp/ccid.c
index 4809753d12aed1c4e6304f02d97e7a301fc44680..f72ca83df552c96252eb851ad5840e07047ad1c0 100644 (file)
--- a/net/dccp/ccid.c
+++ b/net/dccp/ccid.c
@@ -13,6 +13,13 @@
 
 #include "ccid.h"
 
+static u8 builtin_ccids[] = {
+       DCCPC_CCID2,            /* CCID2 is supported by default */
+#if defined(CONFIG_IP_DCCP_CCID3) || defined(CONFIG_IP_DCCP_CCID3_MODULE)
+       DCCPC_CCID3,
+#endif
+};
+
 static struct ccid_operations *ccids[CCID_MAX];
 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
 static atomic_t ccids_lockct = ATOMIC_INIT(0);
@@ -86,6 +93,47 @@ static void ccid_kmem_cache_destroy(struct kmem_cache *slab)
        }
 }
 
+/* check that up to @array_len members in @ccid_array are supported */
+bool ccid_support_check(u8 const *ccid_array, u8 array_len)
+{
+       u8 i, j, found;
+
+       for (i = 0, found = 0; i < array_len; i++, found = 0) {
+               for (j = 0; !found && j < ARRAY_SIZE(builtin_ccids); j++)
+                       found = (ccid_array[i] == builtin_ccids[j]);
+               if (!found)
+                       return false;
+       }
+       return true;
+}
+
+/**
+ * ccid_get_builtin_ccids  -  Provide copy of `builtin' CCID array
+ * @ccid_array: pointer to copy into
+ * @array_len: value to return length into
+ * This function allocates memory - caller must see that it is freed after use.
+ */
+int ccid_get_builtin_ccids(u8 **ccid_array, u8 *array_len)
+{
+       *ccid_array = kmemdup(builtin_ccids, sizeof(builtin_ccids), gfp_any());
+       if (*ccid_array == NULL)
+               return -ENOBUFS;
+       *array_len = ARRAY_SIZE(builtin_ccids);
+       return 0;
+}
+
+int ccid_getsockopt_builtin_ccids(struct sock *sk, int len,
+                                   char __user *optval, int __user *optlen)
+{
+       if (len < sizeof(builtin_ccids))
+               return -EINVAL;
+
+       if (put_user(sizeof(builtin_ccids), optlen) ||
+           copy_to_user(optval, builtin_ccids, sizeof(builtin_ccids)))
+               return -EFAULT;
+       return 0;
+}
+
 int ccid_register(struct ccid_operations *ccid_ops)
 {
        int err = -ENOBUFS;

diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index fdeae7b5731950ed3caa776cf82a0d35f2771012..259f5469d7d04ceacf42d7ff07b260d76a26df1d 100644 (file)
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -103,6 +103,11 @@ static inline void *ccid_priv(const struct ccid *ccid)
        return (void *)ccid->ccid_priv;
 }
 
+extern bool ccid_support_check(u8 const *ccid_array, u8 array_len);
+extern int  ccid_get_builtin_ccids(u8 **ccid_array, u8 *array_len);
+extern int  ccid_getsockopt_builtin_ccids(struct sock *sk, int len,
+                                         char __user *, int __user *);
+
 extern struct ccid *ccid_new(unsigned char id, struct sock *sk, int rx,
                             gfp_t gfp);
 

diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index b859722fba72f619448f0f80c33ae5279fe0db63..9399554878ccc782e3fde891a9d9d89aed7342dd 100644 (file)
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -383,6 +383,10 @@ static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
            !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
                return -EINVAL;
 
+       /* Avoid negotiating alien CCIDs by only advertising supported ones */
+       if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len))
+               return -EOPNOTSUPP;
+
        if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
                return -ENOMEM;
 

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 01332fe7a99a5003917e29962f5e0109973cdbab..b4b10cbd8880b2b088482a257c2e39a2df234ef6 100644 (file)
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -649,6 +649,8 @@ static int do_dccp_getsockopt(struct sock *sk, int level, int optname,
        case DCCP_SOCKOPT_GET_CUR_MPS:
                val = dp->dccps_mss_cache;
                break;
+       case DCCP_SOCKOPT_AVAILABLE_CCIDS:
+               return ccid_getsockopt_builtin_ccids(sk, len, optval, optlen);
        case DCCP_SOCKOPT_SERVER_TIMEWAIT:
                val = dp->dccps_server_timewait;
                break;