esp4: split esp_output_udp_encap and introduce esp_output_encap

Co-developed-by: Herbert Xu <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>
Signed-off-by: Sabrina Dubroca <[e-mail]>
Acked-by: David S. Miller <[e-mail]>
Signed-off-by: Steffen Klassert <[e-mail]>

net/ipv4/esp4.c

···
 	tail[plen - 1] = proto;
 }
 
-static int esp_output_udp_encap(struct xfrm_state *x, struct sk_buff *skb, struct esp_info *esp)
+static struct ip_esp_hdr *esp_output_udp_encap(struct sk_buff *skb,
+					       int encap_type,
+					       struct esp_info *esp,
+					       __be16 sport,
+					       __be16 dport)
 {
-	int encap_type;
 	struct udphdr *uh;
 	__be32 *udpdata32;
-	__be16 sport, dport;
-	struct xfrm_encap_tmpl *encap = x->encap;
-	struct ip_esp_hdr *esph = esp->esph;
 	unsigned int len;
+
+	len = skb->len + esp->tailen - skb_transport_offset(skb);
+	if (len + sizeof(struct iphdr) >= IP_MAX_MTU)
+		return ERR_PTR(-EMSGSIZE);
+
+	uh = (struct udphdr *)esp->esph;
+	uh->source = sport;
+	uh->dest = dport;
+	uh->len = htons(len);
+	uh->check = 0;
+
+	*skb_mac_header(skb) = IPPROTO_UDP;
+
+	if (encap_type == UDP_ENCAP_ESPINUDP_NON_IKE) {
+		udpdata32 = (__be32 *)(uh + 1);
+		udpdata32[0] = udpdata32[1] = 0;
+		return (struct ip_esp_hdr *)(udpdata32 + 2);
+	}
+
+	return (struct ip_esp_hdr *)(uh + 1);
+}
+
+static int esp_output_encap(struct xfrm_state *x, struct sk_buff *skb,
+			    struct esp_info *esp)
+{
+	struct xfrm_encap_tmpl *encap = x->encap;
+	struct ip_esp_hdr *esph;
+	__be16 sport, dport;
+	int encap_type;
 
 	spin_lock_bh(&x->lock);
 	sport = encap->encap_sport;
···
 	encap_type = encap->encap_type;
 	spin_unlock_bh(&x->lock);
 
-	len = skb->len + esp->tailen - skb_transport_offset(skb);
-	if (len + sizeof(struct iphdr) >= IP_MAX_MTU)
-		return -EMSGSIZE;
-
-	uh = (struct udphdr *)esph;
-	uh->source = sport;
-	uh->dest = dport;
-	uh->len = htons(len);
-	uh->check = 0;
-
 	switch (encap_type) {
 	default:
 	case UDP_ENCAP_ESPINUDP:
-		esph = (struct ip_esp_hdr *)(uh + 1);
-		break;
 	case UDP_ENCAP_ESPINUDP_NON_IKE:
-		udpdata32 = (__be32 *)(uh + 1);
-		udpdata32[0] = udpdata32[1] = 0;
-		esph = (struct ip_esp_hdr *)(udpdata32 + 2);
+		esph = esp_output_udp_encap(skb, encap_type, esp, sport, dport);
 		break;
 	}
 
-	*skb_mac_header(skb) = IPPROTO_UDP;
+	if (IS_ERR(esph))
+		return PTR_ERR(esph);
+
 	esp->esph = esph;
 
 	return 0;
···
 
 	/* this is non-NULL only with UDP Encapsulation */
 	if (x->encap) {
-		int err = esp_output_udp_encap(x, skb, esp);
+		int err = esp_output_encap(x, skb, esp);
 
 		if (err < 0)
 			return err;