dccp ccid-2: Schedule Sync as out-of-band mechanism

[net-next-2.6.git] / net / dccp / options.c

diff --git a/net/dccp/options.c b/net/dccp/options.c
index 7743df00f5b13b0e97626cbc87cce14d1ae12291..dabd6ee34d453f56adb20a4fd099bc80d602d201 100644 (file)
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -427,6 +427,7 @@ static 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;
+       struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
        const u16 buflen = dccp_ackvec_buflen(av);
        /* Figure out how many options do we need to represent the ackvec */
        const u8 nr_opts = DIV_ROUND_UP(buflen, DCCP_SINGLE_OPT_MAXLEN);
@@ -435,10 +436,25 @@ static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
        const unsigned char *tail, *from;
        unsigned char *to;
 
-       if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
+       if (dcb->dccpd_opt_len + len > DCCP_MAX_OPT_LEN) {
+               DCCP_WARN("Lacking space for %u bytes on %s packet\n", len,
+                         dccp_packet_name(dcb->dccpd_type));
                return -1;
-
-       DCCP_SKB_CB(skb)->dccpd_opt_len += len;
+       }
+       /*
+        * Since Ack Vectors are variable-length, we can not always predict
+        * their size. To catch exception cases where the space is running out
+        * on the skb, a separate Sync is scheduled to carry the Ack Vector.
+        */
+       if (len > DCCPAV_MIN_OPTLEN &&
+           len + dcb->dccpd_opt_len + skb->len > dp->dccps_mss_cache) {
+               DCCP_WARN("No space left for Ack Vector (%u) on skb (%u+%u), "
+                         "MPS=%u ==> reduce payload size?\n", len, skb->len,
+                         dcb->dccpd_opt_len, dp->dccps_mss_cache);
+               dp->dccps_sync_scheduled = 1;
+               return 0;
+       }
+       dcb->dccpd_opt_len += len;
 
        to   = skb_push(skb, len);
        len  = buflen;
@@ -479,7 +495,7 @@ static int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
        /*
         * Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
         */
-       if (dccp_ackvec_update_records(av, DCCP_SKB_CB(skb)->dccpd_seq, nonce))
+       if (dccp_ackvec_update_records(av, dcb->dccpd_seq, nonce))
                return -ENOBUFS;
        return 0;
 }