[DCCP]: Factor out common code for generating Resets

This factors code common to dccp_v{4,6}_ctl_send_reset into a separate function,
and adds support for filling in the Data 1 ... Data 3 fields from RFC 4340, 5.6.

It is useful to have this separate, since the following Reset codes will always
be generated from the control socket rather than via dccp_send_reset:
 * Code 3, "No Connection", cf. 8.3.1;
 * Code 4, "Packet Error" (identification for Data 1 added);
 * Code 5, "Option Error" (identification for Data 1..3 added, will be used later);
 * Code 6, "Mandatory Error" (same as Option Error);
 * Code 7, "Connection Refused" (what on Earth is the difference to "No Connection"?);
 * Code 8, "Bad Service Code";
 * Code 9, "Too Busy";
 * Code 10, "Bad Init Cookie" (not used).

Code 0 is not recommended by the RFC, the following codes would be used in
dccp_send_reset() instead, since they all relate to an established DCCP connection:
 * Code 1, "Closed";
 * Code 2, "Aborted";
 * Code 11, "Aggression Penalty" (12.3).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

1 files changed, 5 insertions, 33 deletions

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 58a79c2ae55c..2312b9f4d7af 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -510,17 +510,12 @@ out:
 static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 {
         int err;
-        struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
         const struct iphdr *rxiph;
-        const int dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
-                                       sizeof(struct dccp_hdr_ext) +
-                                       sizeof(struct dccp_hdr_reset);
         struct sk_buff *skb;
         struct dst_entry *dst;
-        u64 seqno = 0;
 
         /* Never send a reset in response to a reset. */
-        if (rxdh->dccph_type == DCCP_PKT_RESET)
+        if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
                 return;
 
         if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
@@ -530,37 +525,14 @@ static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
         if (dst == NULL)
                 return;
 
-        skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header,
-                        GFP_ATOMIC);
+        skb = dccp_ctl_make_reset(dccp_v4_ctl_socket, rxskb);
         if (skb == NULL)
                 goto out;
 
-        /* Reserve space for headers. */
-        skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
-        skb->dst = dst_clone(dst);
-
-        dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
-
-        /* Build DCCP header and checksum it. */
-        dh->dccph_type     = DCCP_PKT_RESET;
-        dh->dccph_sport    = rxdh->dccph_dport;
-        dh->dccph_dport    = rxdh->dccph_sport;
-        dh->dccph_doff     = dccp_hdr_reset_len / 4;
-        dh->dccph_x        = 1;
-        dccp_hdr_reset(skb)->dccph_reset_code =
-                                DCCP_SKB_CB(rxskb)->dccpd_reset_code;
-
-        /* See "8.3.1. Abnormal Termination" in RFC 4340 */
-        if (DCCP_SKB_CB(rxskb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
-                seqno = ADD48(DCCP_SKB_CB(rxskb)->dccpd_ack_seq, 1);
-
-        dccp_hdr_set_seq(dh, seqno);
-        dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), DCCP_SKB_CB(rxskb)->dccpd_seq);
-
-        dccp_csum_outgoing(skb);
         rxiph = ip_hdr(rxskb);
-        dh->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
-                                                 rxiph->daddr);
+        dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
+                                                                 rxiph->daddr);
+        skb->dst = dst_clone(dst);
 
         bh_lock_sock(dccp_v4_ctl_socket->sk);
         err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,