[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>

1 files changed, 32 insertions, 14 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 41d34d1babc1..bdf1bb7a82c0 100644
--- 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:
          *