[DCCP]: Combine allocating & zeroing header space on skb

This is a code simplification:
it combines three often recurring operations into one inline function,

        * allocate `len' bytes header space in skb
        * fill these `len' bytes with zeroes
        * cast the start of this header space as dccp_hdr

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

include/linux/dccp.h

@@ -256,6 +256,13 @@ static inline struct dccp_hdr *dccp_hdr(const struct sk_buff *skb)
 	return (struct dccp_hdr *)skb->h.raw;
 }
 
+static inline struct dccp_hdr *dccp_zeroed_hdr(struct sk_buff *skb, int headlen)
+{
+	skb->h.raw = skb_push(skb, headlen);
+	memset(skb->h.raw, 0, headlen);
+	return dccp_hdr(skb);
+}
+
 static inline struct dccp_hdr_ext *dccp_hdrx(const struct sk_buff *skb)
 {
 	return (struct dccp_hdr_ext *)(skb->h.raw + sizeof(struct dccp_hdr));

net/dccp/ipv4.c

@@ -212,12 +212,9 @@ static void dccp_v4_reqsk_send_ack(struct sk_buff *rxskb,
 
 	/* Reserve space for headers. */
 	skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
-
 	skb->dst = dst_clone(rxskb->dst);
 
-	skb->h.raw = skb_push(skb, dccp_hdr_ack_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_ack_len);
+	dh = dccp_zeroed_hdr(skb, dccp_hdr_ack_len);
 
 	/* Build DCCP header and checksum it. */
 	dh->dccph_type	   = DCCP_PKT_ACK;
@@ -720,9 +717,7 @@ static void dccp_v4_ctl_send_reset(struct sk_buff *rxskb)
 	skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
 	skb->dst = dst_clone(dst);
 
-	skb->h.raw = skb_push(skb, dccp_hdr_reset_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_reset_len);
+	dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 
 	/* Build DCCP header and checksum it. */
 	dh->dccph_type	   = DCCP_PKT_RESET;

net/dccp/ipv6.c

@@ -537,9 +537,7 @@ static void dccp_v6_ctl_send_reset(struct sk_buff *rxskb)
 
 	skb_reserve(skb, dccp_v6_ctl_socket->sk->sk_prot->max_header);
 
-	skb->h.raw = skb_push(skb, dccp_hdr_reset_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_reset_len);
+	dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
 
 	/* Swap the send and the receive. */
 	dh->dccph_type	= DCCP_PKT_RESET;
@@ -601,9 +599,7 @@ static void dccp_v6_reqsk_send_ack(struct sk_buff *rxskb,
 
 	skb_reserve(skb, dccp_v6_ctl_socket->sk->sk_prot->max_header);
 
-	skb->h.raw = skb_push(skb, dccp_hdr_ack_len);
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_hdr_ack_len);
+	dh = dccp_zeroed_hdr(skb, dccp_hdr_ack_len);
 
 	/* Build DCCP header and checksum it. */
 	dh->dccph_type	= DCCP_PKT_ACK;

net/dccp/output.c

@@ -88,11 +88,9 @@ static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
 			return -EPROTO;
 		}
 
-		skb->h.raw = skb_push(skb, dccp_header_size);
-		dh = dccp_hdr(skb);
 
 		/* Build DCCP header and checksum it. */
-		memset(dh, 0, dccp_header_size);
+		dh = dccp_zeroed_hdr(skb, dccp_header_size);
 		dh->dccph_type	= dcb->dccpd_type;
 		dh->dccph_sport	= inet->sport;
 		dh->dccph_dport	= inet->dport;
@@ -340,10 +338,7 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 		return NULL;
 	}
 
-	skb->h.raw = skb_push(skb, dccp_header_size);
-
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_header_size);
+	dh = dccp_zeroed_hdr(skb, dccp_header_size);
 
 	dh->dccph_sport	= inet_sk(sk)->sport;
 	dh->dccph_dport	= inet_rsk(req)->rmt_port;
@@ -392,10 +387,7 @@ static struct sk_buff *dccp_make_reset(struct sock *sk, struct dst_entry *dst,
 		return NULL;
 	}
 
-	skb->h.raw = skb_push(skb, dccp_header_size);
-
-	dh = dccp_hdr(skb);
-	memset(dh, 0, dccp_header_size);
+	dh = dccp_zeroed_hdr(skb, dccp_header_size);
 
 	dh->dccph_sport	= inet_sk(sk)->sport;
 	dh->dccph_dport	= inet_sk(sk)->dport;