after this I get:

$ diff-funcs tcp_v6_send_reset tcp_ipv6.c tcp_ipv6.c tcp_v6_send_ack
 --- tcp_ipv6.c:tcp_v6_send_reset()
 +++ tcp_ipv6.c:tcp_v6_send_ack()
@@ -1,4 +1,5 @@
-static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb)
+static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack, u32 win,
u32 ts,
+                           struct tcp_md5sig_key *key)
 {
        struct tcphdr *th = tcp_hdr(skb), *t1;
        struct sk_buff *buff;
@@ -7,31 +8,14 @@
        struct sock *ctl_sk = net->ipv6.tcp_sk;
        unsigned int tot_len = sizeof(struct tcphdr);
        __be32 *topt;
-#ifdef CONFIG_TCP_MD5SIG
-       struct tcp_md5sig_key *key;
-#endif
-
-       if (th->rst)
-               return;
-
-       if (!ipv6_unicast_destination(skb))
-               return;

+       if (ts)
+               tot_len += TCPOLEN_TSTAMP_ALIGNED;
 #ifdef CONFIG_TCP_MD5SIG
-       if (sk)
-               key = tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr);
-       else
-               key = NULL;
-
        if (key)
                tot_len += TCPOLEN_MD5SIG_ALIGNED;
 #endif

-       /*
-        * We need to grab some memory, and put together an RST,
-        * and then put it into the queue to be sent.
-        */
-
        buff = alloc_skb(MAX_HEADER + sizeof(struct ipv6hdr) + tot_len,
                         GFP_ATOMIC);
        if (buff == NULL)
@@ -46,18 +30,20 @@
        t1->dest = th->source;
        t1->source = th->dest;
        t1->doff = tot_len / 4;
-       t1->rst = 1;
-
-       if(th->ack) {
-               t1->seq = th->ack_seq;
-       } else {
-               t1->ack = 1;
-               t1->ack_seq = htonl(ntohl(th->seq) + th->syn + th->fin
-                                   + skb->len - (th->doff<<2));
-       }
+       t1->seq = htonl(seq);
+       t1->ack_seq = htonl(ack);
+       t1->ack = 1;
+       t1->window = htons(win);

        topt = (__be32 *)(t1 + 1);

+       if (ts) {
+               *topt++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
+                               (TCPOPT_TIMESTAMP << 8) |
TCPOLEN_TIMESTAMP);
+               *topt++ = htonl(tcp_time_stamp);
+               *topt++ = htonl(ts);
+       }
+
 #ifdef CONFIG_TCP_MD5SIG
        if (key) {
                *topt++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
@@ -84,15 +70,10 @@
        fl.fl_ip_sport = t1->source;
        security_skb_classify_flow(skb, &fl);

-       /* Pass a socket to ip6_dst_lookup either it is for RST
-        * Underlying function will use this to retrieve the network
-        * namespace
-        */
        if (!ip6_dst_lookup(ctl_sk, &buff->dst, &fl)) {
                if (xfrm_lookup(&buff->dst, &fl, NULL, 0) >= 0) {
                        ip6_xmit(ctl_sk, buff, &fl, NULL, 0);
                        TCP_INC_STATS_BH(net, TCP_MIB_OUTSEGS);
-                       TCP_INC_STATS_BH(net, TCP_MIB_OUTRSTS);
                        return;
                }
        }


...which starts to be trivial to combine.
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>