6 files changed, 61 insertions, 8 deletions

diff --git a/Documentation/networking/dccp.txt b/Documentation/networking/dccp.txt
index 43df4487379b..610083ff73f6 100644
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -61,6 +61,20 @@ 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_CCID is write-only and sets both the TX and RX CCIDs at the same
+time, combining the operation of the next two socket options. This option is
+preferrable over the latter two, since often applications will use the same
+type of CCID for both directions; and mixed use of CCIDs is not currently well
+understood. This socket option takes as argument at least one uint8_t value, or
+an array of uint8_t values, which must match available CCIDS (see above). CCIDs
+must be registered on the socket before calling connect() or listen().
+
+DCCP_SOCKOPT_TX_CCID is read/write. It returns the current CCID (if set) or sets
+the preference list for the TX CCID, using the same format as DCCP_SOCKOPT_CCID.
+Please note that the getsockopt argument type here is `int', not uint8_t.
+
+DCCP_SOCKOPT_RX_CCID is analogous to DCCP_SOCKOPT_TX_CCID, but for the RX CCID.
+
 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 eda389ce04f4..6a72ff52a8a4 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -168,6 +168,8 @@ enum {
         DCCPO_MIN_CCID_SPECIFIC = 128,
         DCCPO_MAX_CCID_SPECIFIC = 255,
 };
+/* maximum size of a single TLV-encoded DCCP option (sans type/len bytes) */
+#define DCCP_SINGLE_OPT_MAXLEN  253
 
 /* DCCP CCIDS */
 enum {
@@ -203,6 +205,9 @@ enum dccp_feature_numbers {
 #define DCCP_SOCKOPT_SEND_CSCOV         10
 #define DCCP_SOCKOPT_RECV_CSCOV         11
 #define DCCP_SOCKOPT_AVAILABLE_CCIDS    12
+#define DCCP_SOCKOPT_CCID               13
+#define DCCP_SOCKOPT_TX_CCID            14
+#define DCCP_SOCKOPT_RX_CCID            15
 #define DCCP_SOCKOPT_CCID_RX_INFO       128
 #define DCCP_SOCKOPT_CCID_TX_INFO       192
 
diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 1e8be246ad15..01e4d39fa232 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -12,7 +12,6 @@
 #include "ackvec.h"
 #include "dccp.h"
 
-#include <linux/dccp.h>
 #include <linux/init.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
@@ -68,7 +67,7 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
         struct dccp_sock *dp = dccp_sk(sk);
         struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
         /* Figure out how many options do we need to represent the ackvec */
-        const u16 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_MAX_ACKVEC_OPT_LEN);
+        const u8 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_SINGLE_OPT_MAXLEN);
         u16 len = av->av_vec_len + 2 * nr_opts, i;
         u32 elapsed_time;
         const unsigned char *tail, *from;
@@ -100,8 +99,8 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
         for (i = 0; i < nr_opts; ++i) {
                 int copylen = len;
 
-                if (len > DCCP_MAX_ACKVEC_OPT_LEN)
-                        copylen = DCCP_MAX_ACKVEC_OPT_LEN;
+                if (len > DCCP_SINGLE_OPT_MAXLEN)
+                        copylen = DCCP_SINGLE_OPT_MAXLEN;
 
                 *to++ = DCCPO_ACK_VECTOR_0;
                 *to++ = copylen + 2;
@@ -432,7 +431,7 @@ found:
 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
                       u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 {
-        if (len > DCCP_MAX_ACKVEC_OPT_LEN)
+        if (len > DCCP_SINGLE_OPT_MAXLEN)
                 return -1;
 
         /* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h
index bcb64fb4acef..4ccee030524e 100644
--- a/net/dccp/ackvec.h
+++ b/net/dccp/ackvec.h
@@ -11,15 +11,14 @@
  *      published by the Free Software Foundation.
  */
 
+#include <linux/dccp.h>
 #include <linux/compiler.h>
 #include <linux/ktime.h>
 #include <linux/list.h>
 #include <linux/types.h>
 
-/* Read about the ECN nonce to see why it is 253 */
-#define DCCP_MAX_ACKVEC_OPT_LEN 253
 /* We can spread an ack vector across multiple options */
-#define DCCP_MAX_ACKVEC_LEN (DCCP_MAX_ACKVEC_OPT_LEN * 2)
+#define DCCP_MAX_ACKVEC_LEN (DCCP_SINGLE_OPT_MAXLEN * 2)
 
 #define DCCP_ACKVEC_STATE_RECEIVED      0
 #define DCCP_ACKVEC_STATE_ECN_MARKED    (1 << 6)
diff --git a/net/dccp/feat.h b/net/dccp/feat.h
index 4d172822df17..093af1610d11 100644
--- a/net/dccp/feat.h
+++ b/net/dccp/feat.h
@@ -22,6 +22,8 @@
 /* Wmin=32 and Wmax=2^46-1 from 7.5.2 */
 #define DCCPF_SEQ_WMIN          32
 #define DCCPF_SEQ_WMAX          0x3FFFFFFFFFFFull
+/* Maximum number of SP values that fit in a single (Confirm) option */
+#define DCCP_FEAT_MAX_SP_VALS   (DCCP_SINGLE_OPT_MAXLEN - 2)
 
 enum dccp_feat_type {
         FEAT_AT_RX   = 1,       /* located at RX side of half-connection  */
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 8b63394ec24c..445884cf1c29 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -501,6 +501,36 @@ static int dccp_setsockopt_cscov(struct sock *sk, int cscov, bool rx)
         return rc;
 }
 
+static int dccp_setsockopt_ccid(struct sock *sk, int type,
+                                char __user *optval, int optlen)
+{
+        u8 *val;
+        int rc = 0;
+
+        if (optlen < 1 || optlen > DCCP_FEAT_MAX_SP_VALS)
+                return -EINVAL;
+
+        val = kmalloc(optlen, GFP_KERNEL);
+        if (val == NULL)
+                return -ENOMEM;
+
+        if (copy_from_user(val, optval, optlen)) {
+                kfree(val);
+                return -EFAULT;
+        }
+
+        lock_sock(sk);
+        if (type == DCCP_SOCKOPT_TX_CCID || type == DCCP_SOCKOPT_CCID)
+                rc = dccp_feat_register_sp(sk, DCCPF_CCID, 1, val, optlen);
+
+        if (!rc && (type == DCCP_SOCKOPT_RX_CCID || type == DCCP_SOCKOPT_CCID))
+                rc = dccp_feat_register_sp(sk, DCCPF_CCID, 0, val, optlen);
+        release_sock(sk);
+
+        kfree(val);
+        return rc;
+}
+
 static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
                 char __user *optval, int optlen)
 {
@@ -515,6 +545,10 @@ static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
         case DCCP_SOCKOPT_CHANGE_R:
                 DCCP_WARN("sockopt(CHANGE_L/R) is deprecated: fix your app\n");
                 return 0;
+        case DCCP_SOCKOPT_CCID:
+        case DCCP_SOCKOPT_RX_CCID:
+        case DCCP_SOCKOPT_TX_CCID:
+                return dccp_setsockopt_ccid(sk, optname, optval, optlen);
         }
 
         if (optlen < (int)sizeof(int))