net: udp4: move GSO functions to udp_offload

Similarly to TCP offloading and UDPv6 offloading, move all related
UDPv4 functions to udp_offload.c to make things more explicit. Also,
by this, we can make those functions static.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 100 insertions, 0 deletions

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
new file mode 100644
index 000000000000..f35eccaa855e
--- /dev/null
+++ b/net/ipv4/udp_offload.c
@@ -0,0 +1,100 @@
+/*
+ *	IPV4 GSO/GRO offload support
+ *	Linux INET implementation
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ *	UDPv4 GSO support
+ */
+
+#include <linux/skbuff.h>
+#include <net/udp.h>
+#include <net/protocol.h>
+
+static int udp4_ufo_send_check(struct sk_buff *skb)
+{
+	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
+		return -EINVAL;
+
+	if (likely(!skb->encapsulation)) {
+		const struct iphdr *iph;
+		struct udphdr *uh;
+
+		iph = ip_hdr(skb);
+		uh = udp_hdr(skb);
+
+		uh->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, skb->len,
+				IPPROTO_UDP, 0);
+		skb->csum_start = skb_transport_header(skb) - skb->head;
+		skb->csum_offset = offsetof(struct udphdr, check);
+		skb->ip_summed = CHECKSUM_PARTIAL;
+	}
+
+	return 0;
+}
+
+static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
+					 netdev_features_t features)
+{
+	struct sk_buff *segs = ERR_PTR(-EINVAL);
+	unsigned int mss;
+
+	mss = skb_shinfo(skb)->gso_size;
+	if (unlikely(skb->len <= mss))
+		goto out;
+
+	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
+		/* Packet is from an untrusted source, reset gso_segs. */
+		int type = skb_shinfo(skb)->gso_type;
+
+		if (unlikely(type & ~(SKB_GSO_UDP | SKB_GSO_DODGY |
+				      SKB_GSO_UDP_TUNNEL |
+				      SKB_GSO_GRE | SKB_GSO_MPLS) ||
+			     !(type & (SKB_GSO_UDP))))
+			goto out;
+
+		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
+
+		segs = NULL;
+		goto out;
+	}
+
+	/* Fragment the skb. IP headers of the fragments are updated in
+	 * inet_gso_segment()
+	 */
+	if (skb->encapsulation && skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
+		segs = skb_udp_tunnel_segment(skb, features);
+	else {
+		int offset;
+		__wsum csum;
+
+		/* Do software UFO. Complete and fill in the UDP checksum as
+		 * HW cannot do checksum of UDP packets sent as multiple
+		 * IP fragments.
+		 */
+		offset = skb_checksum_start_offset(skb);
+		csum = skb_checksum(skb, offset, skb->len - offset, 0);
+		offset += skb->csum_offset;
+		*(__sum16 *)(skb->data + offset) = csum_fold(csum);
+		skb->ip_summed = CHECKSUM_NONE;
+
+		segs = skb_segment(skb, features);
+	}
+out:
+	return segs;
+}
+
+static const struct net_offload udpv4_offload = {
+	.callbacks = {
+		.gso_send_check = udp4_ufo_send_check,
+		.gso_segment = udp4_ufo_fragment,
+	},
+};
+
+int __init udpv4_offload_init(void)
+{
+	return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
+}