: Factor out common code for generating Resets

[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).

---
 net/dccp/dccp.h   |    2 ++
 net/dccp/ipv4.c   |   38 +++++---------------------------------
 net/dccp/ipv6.c   |   39 ++++++---------------------------------
 net/dccp/output.c |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 65 insertions(+), 66 deletions(-)

@@ -298,6 +298,8 @@ extern unsigned int dccp_poll(struct fil
 extern int	   dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
 				   int addr_len);
 
+extern struct sk_buff *
+		   dccp_ctl_make_reset(struct socket *ctl, struct sk_buff *skb);
 extern int	   dccp_send_reset(struct sock *sk, enum dccp_reset_codes code);
 extern void	   dccp_send_close(struct sock *sk, const int active);
 extern int	   dccp_invalid_packet(struct sk_buff *skb);

@@ -512,17 +512,12 @@ 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)

@@ -532,37 +527,14 @@ static void dccp_v4_ctl_send_reset(struc
 	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,
--- a/net/dccp/ipv6.c

+++ b/net/dccp/ipv6.c
@@ -301,50 +301,23 @@ static void dccp_v6_reqsk_destructor(str

static void dccp_v6_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb) {
- struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
struct ipv6hdr *rxip6h;
- const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
- sizeof(struct dccp_hdr_ext) +
- sizeof(struct dccp_hdr_reset);
struct sk_buff *skb;
struct flowi fl;
- u64 seqno = 0;

- if (rxdh->dccph_type = DCCP_PKT_RESET)
+ if (dccp_hdr(rxskb)->dccph_type = DCCP_PKT_RESET)
return;

if (!ipv6_unicast_destination(rxskb))
return;

- skb = alloc_skb(dccp_v6_ctl_socket->sk->sk_prot->max_header,
- GFP_ATOMIC);
+ skb = dccp_ctl_make_reset(dccp_v6_ctl_socket, rxskb);
if (skb = NULL)
return;

- skb_reserve(skb, dccp_v6_ctl_socket->sk->sk_prot->max_header);
-
- dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
-
- /* Swap the send and the receive. */
- 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);
rxip6h = ipv6_hdr(rxskb);
- dh->dccph_checksum = dccp_v6_csum_finish(skb, &rxip6h->saddr,
- &rxip6h->daddr);
+ dccp_hdr(skb)->dccph_checksum = dccp_v6_csum_finish(skb, &rxip6h->saddr,
+ &rxip6h->daddr);

memset(&fl, 0, sizeof(fl)); ipv6_addr_copy(&fl.fl6_dst, &rxip6h->saddr);
@@ -352,8 +325,8 @@ static void dccp_v6_ctl_send_reset(struc

fl.proto = IPPROTO_DCCP;
fl.oif = inet6_iif(rxskb);
- fl.fl_ip_dport = dh->dccph_dport;
- fl.fl_ip_sport = dh->dccph_sport;
+ fl.fl_ip_dport = dccp_hdr(skb)->dccph_dport;
+ fl.fl_ip_sport = dccp_hdr(skb)->dccph_sport;
security_skb_classify_flow(rxskb, &fl);

/* sk = NULL, but it is safe for now. RST socket required. */