netpoll: move Ethernet setup to push_eth() helper

Refactor Ethernet header population into dedicated function, completing
the layered abstraction with:

- push_eth() for link layer
- push_udp() for transport
- push_ipv4()/push_ipv6() for network

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: NipaLocal <nipa@local>

Author: leitao

net/core/netpoll.c

@@ -417,7 +417,6 @@ EXPORT_SYMBOL(netpoll_send_skb);
 static void push_ipv6(struct netpoll *np, struct sk_buff *skb, int len)
 {
 	struct ipv6hdr *ip6h;
-	struct ethhdr *eth;
 
 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
@@ -435,16 +434,12 @@ static void push_ipv6(struct netpoll *np, struct sk_buff *skb, int len)
 	ip6h->saddr = np->local_ip.in6;
 	ip6h->daddr = np->remote_ip.in6;
 
-	eth = skb_push(skb, ETH_HLEN);
-	skb_reset_mac_header(skb);
 	skb->protocol = htons(ETH_P_IPV6);
-	eth->h_proto = htons(ETH_P_IPV6);
 }
 
 static void push_ipv4(struct netpoll *np, struct sk_buff *skb, int len)
 {
 	static atomic_t ip_ident;
-	struct ethhdr *eth;
 	struct iphdr *iph;
 	int ip_len;
 
@@ -466,11 +461,7 @@ static void push_ipv4(struct netpoll *np, struct sk_buff *skb, int len)
 	put_unaligned(np->local_ip.ip, &iph->saddr);
 	put_unaligned(np->remote_ip.ip, &iph->daddr);
 	iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
-
-	eth = skb_push(skb, ETH_HLEN);
-	skb_reset_mac_header(skb);
 	skb->protocol = htons(ETH_P_IP);
-	eth->h_proto = htons(ETH_P_IP);
 }
 
 static void push_udp(struct netpoll *np, struct sk_buff *skb, int len)
@@ -491,11 +482,24 @@ static void push_udp(struct netpoll *np, struct sk_buff *skb, int len)
 	netpoll_udp_checksum(np, skb, len);
 }
 
+static void push_eth(struct netpoll *np, struct sk_buff *skb)
+{
+	struct ethhdr *eth;
+
+	eth = skb_push(skb, ETH_HLEN);
+	skb_reset_mac_header(skb);
+	ether_addr_copy(eth->h_source, np->dev->dev_addr);
+	ether_addr_copy(eth->h_dest, np->remote_mac);
+	if (np->ipv6)
+		eth->h_proto = htons(ETH_P_IPV6);
+	else
+		eth->h_proto = htons(ETH_P_IP);
+}
+
 int netpoll_send_udp(struct netpoll *np, const char *msg, int len)
 {
 	int total_len, ip_len, udp_len;
 	struct sk_buff *skb;
-	struct ethhdr *eth;
 
 	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
 		WARN_ON_ONCE(!irqs_disabled());
@@ -521,11 +525,7 @@ int netpoll_send_udp(struct netpoll *np, const char *msg, int len)
 		push_ipv6(np, skb, len);
 	else
 		push_ipv4(np, skb, len);
-
-	eth = eth_hdr(skb);
-	ether_addr_copy(eth->h_source, np->dev->dev_addr);
-	ether_addr_copy(eth->h_dest, np->remote_mac);
-
+	push_eth(np, skb);
 	skb->dev = np->dev;
 
 	return (int)netpoll_send_skb(np, skb);