[DCCP] ackvec: Split long ack vectors across multiple options

Ack vectors grow proportional to the window size.  If an ack vector does not fit
into a single option, it must be spread across multiple options.  This patch
will allow for windows to grow larger.

Committer note: Simplified the patch a bit, original algorithm kept.

Signed-off-by: Andrea Bittau <a.bittau@cs.ucl.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 41d34d1babc17da94d874a75878c66cc9fc5cb87..bdf1bb7a82c0758725522b69e7d73fe2663332e6 100644 (file)
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -68,10 +68,15 @@ 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;
-       int len = av->dccpav_vec_len + 2;
+       /* Figure out how many options do we need to represent the ackvec */
+       const u16 nr_opts = (av->dccpav_vec_len +
+                            DCCP_MAX_ACKVEC_OPT_LEN - 1) /
+                           DCCP_MAX_ACKVEC_OPT_LEN;
+       u16 len = av->dccpav_vec_len + 2 * nr_opts, i;
        struct timeval now;
        u32 elapsed_time;
-       unsigned char *to, *from;
+       const unsigned char *tail, *from;
+       unsigned char *to;
        struct dccp_ackvec_record *avr;
 
        if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
@@ -90,24 +95,37 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 
        DCCP_SKB_CB(skb)->dccpd_opt_len += len;
 
-       to    = skb_push(skb, len);
-       *to++ = DCCPO_ACK_VECTOR_0;
-       *to++ = len;
-
+       to   = skb_push(skb, len);
        len  = av->dccpav_vec_len;
        from = av->dccpav_buf + av->dccpav_buf_head;
+       tail = av->dccpav_buf + DCCP_MAX_ACKVEC_LEN;
+
+       for (i = 0; i < nr_opts; ++i) {
+               int copylen = len;
+
+               if (len > DCCP_MAX_ACKVEC_OPT_LEN)
+                       copylen = DCCP_MAX_ACKVEC_OPT_LEN;
 
-       /* Check if buf_head wraps */
-       if ((int)av->dccpav_buf_head + len > DCCP_MAX_ACKVEC_LEN) {
-               const u32 tailsize = DCCP_MAX_ACKVEC_LEN - av->dccpav_buf_head;
+               *to++ = DCCPO_ACK_VECTOR_0;
+               *to++ = copylen + 2;
+
+               /* Check if buf_head wraps */
+               if (from + copylen > tail) {
+                       const u16 tailsize = tail - from;
+
+                       memcpy(to, from, tailsize);
+                       to      += tailsize;
+                       len     -= tailsize;
+                       copylen -= tailsize;
+                       from    = av->dccpav_buf;
+               }
 
-               memcpy(to, from, tailsize);
-               to   += tailsize;
-               len  -= tailsize;
-               from = av->dccpav_buf;
+               memcpy(to, from, copylen);
+               from += copylen;
+               to   += copylen;
+               len  -= copylen;
        }
 
-       memcpy(to, from, len);
        /*
         *      From RFC 4340, A.2:
         *