dccp: Feature negotiation for minimum-checksum-coverage

This provides feature negotiation for server minimum checksum coverage
which so far has been missing.

Since sender/receiver coverage values range only from 0...15, their
type has also been reduced in size from u16 to u4.

Feature-negotiation options are now generated for both sender and receiver
coverage, i.e. when the peer has `forgotten' to enable partial coverage
then feature negotiation will automatically enable (negotiate) the partial
coverage value for this connection.

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

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index 6eaaca9..5a5a899 100644 (file)
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -527,8 +527,8 @@ struct dccp_sock {
        __u32                           dccps_timestamp_time;
        __u16                           dccps_l_ack_ratio;
        __u16                           dccps_r_ack_ratio;
-       __u16                           dccps_pcslen;
-       __u16                           dccps_pcrlen;
+       __u8                            dccps_pcslen:4;
+       __u8                            dccps_pcrlen:4;
        __u64                           dccps_ndp_count:48;
        unsigned long                   dccps_rate_last;
        struct dccp_minisock            dccps_minisock;

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 3090fc4..c6b4362 100644 (file)
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -470,6 +470,42 @@ static int dccp_setsockopt_service(struct sock *sk, const __be32 service,
        return 0;
 }
 
+static int dccp_setsockopt_cscov(struct sock *sk, int cscov, bool rx)
+{
+       u8 *list, len;
+       int i, rc;
+
+       if (cscov < 0 || cscov > 15)
+               return -EINVAL;
+       /*
+        * Populate a list of permissible values, in the range cscov...15. This
+        * is necessary since feature negotiation of single values only works if
+        * both sides incidentally choose the same value. Since the list starts
+        * lowest-value first, negotiation will pick the smallest shared value.
+        */
+       if (cscov == 0)
+               return 0;
+       len = 16 - cscov;
+
+       list = kmalloc(len, GFP_KERNEL);
+       if (list == NULL)
+               return -ENOBUFS;
+
+       for (i = 0; i < len; i++)
+               list[i] = cscov++;
+
+       rc = dccp_feat_register_sp(sk, DCCPF_MIN_CSUM_COVER, rx, list, len);
+
+       if (rc == 0) {
+               if (rx)
+                       dccp_sk(sk)->dccps_pcrlen = cscov;
+               else
+                       dccp_sk(sk)->dccps_pcslen = cscov;
+       }
+       kfree(list);
+       return rc;
+}
+
 static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
                char __user *optval, int optlen)
 {
@@ -502,20 +538,11 @@ static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
                else
                        dp->dccps_server_timewait = (val != 0);
                break;
-       case DCCP_SOCKOPT_SEND_CSCOV:   /* sender side, RFC 4340, sec. 9.2 */
-               if (val < 0 || val > 15)
-                       err = -EINVAL;
-               else
-                       dp->dccps_pcslen = val;
+       case DCCP_SOCKOPT_SEND_CSCOV:
+               err = dccp_setsockopt_cscov(sk, val, false);
                break;
-       case DCCP_SOCKOPT_RECV_CSCOV:   /* receiver side, RFC 4340 sec. 9.2.1 */
-               if (val < 0 || val > 15)
-                       err = -EINVAL;
-               else {
-                       dp->dccps_pcrlen = val;
-                       /* FIXME: add feature negotiation,
-                        * ChangeL(MinimumChecksumCoverage, val) */
-               }
+       case DCCP_SOCKOPT_RECV_CSCOV:
+               err = dccp_setsockopt_cscov(sk, val, true);
                break;
        default:
                err = -ENOPROTOOPT;