net: Add driver helper functions to determine checksum offloadability

Add skb_csum_offload_chk driver helper function to determine if a
device with limited checksum offload capabilities is able to offload the
checksum for a given packet.

This patch includes:
  - The skb_csum_offload_chk function. Returns true if checksum is
    offloadable, else false. Optionally, in the case that the checksum
    is not offloable, the function can call skb_checksum_help to resolve
    the checksum. skb_csum_offload_chk also returns whether the checksum
    refers to an encapsulated checksum.
  - Definition of skb_csum_offl_spec structure that caller uses to
    indicate rules about what it can offload (e.g. IPv4/v6, TCP/UDP only,
    whether encapsulated checksums can be offloaded, whether checksum with
    IPv6 extension headers can be offloaded).
  - Ancilary functions called skb_csum_offload_chk_help,
    skb_csum_off_chk_help_cmn, skb_csum_off_chk_help_cmn_v4_only.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 78 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 283984b67cd9..9fb6395967de 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2522,6 +2522,71 @@ static inline void skb_gro_remcsum_cleanup(struct sk_buff *skb,
 	remcsum_unadjust((__sum16 *)ptr, grc->delta);
 }
 
+struct skb_csum_offl_spec {
+	__u16		ipv4_okay:1,
+			ipv6_okay:1,
+			encap_okay:1,
+			ip_options_okay:1,
+			ext_hdrs_okay:1,
+			tcp_okay:1,
+			udp_okay:1,
+			sctp_okay:1,
+			vlan_okay:1,
+			no_encapped_ipv6:1,
+			no_not_encapped:1;
+};
+
+bool __skb_csum_offload_chk(struct sk_buff *skb,
+			    const struct skb_csum_offl_spec *spec,
+			    bool *csum_encapped,
+			    bool csum_help);
+
+static inline bool skb_csum_offload_chk(struct sk_buff *skb,
+					const struct skb_csum_offl_spec *spec,
+					bool *csum_encapped,
+					bool csum_help)
+{
+	if (skb->ip_summed != CHECKSUM_PARTIAL)
+		return false;
+
+	return __skb_csum_offload_chk(skb, spec, csum_encapped, csum_help);
+}
+
+static inline bool skb_csum_offload_chk_help(struct sk_buff *skb,
+					     const struct skb_csum_offl_spec *spec)
+{
+	bool csum_encapped;
+
+	return skb_csum_offload_chk(skb, spec, &csum_encapped, true);
+}
+
+static inline bool skb_csum_off_chk_help_cmn(struct sk_buff *skb)
+{
+	static const struct skb_csum_offl_spec csum_offl_spec = {
+		.ipv4_okay = 1,
+		.ip_options_okay = 1,
+		.ipv6_okay = 1,
+		.vlan_okay = 1,
+		.tcp_okay = 1,
+		.udp_okay = 1,
+	};
+
+	return skb_csum_offload_chk_help(skb, &csum_offl_spec);
+}
+
+static inline bool skb_csum_off_chk_help_cmn_v4_only(struct sk_buff *skb)
+{
+	static const struct skb_csum_offl_spec csum_offl_spec = {
+		.ipv4_okay = 1,
+		.ip_options_okay = 1,
+		.tcp_okay = 1,
+		.udp_okay = 1,
+		.vlan_okay = 1,
+	};
+
+	return skb_csum_offload_chk_help(skb, &csum_offl_spec);
+}
+
 static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
 				  unsigned short type,
 				  const void *daddr, const void *saddr,
@@ -3711,6 +3776,19 @@ static inline bool can_checksum_protocol(netdev_features_t features,
 	}
 }
 
+/* Map an ethertype into IP protocol if possible */
+static inline int eproto_to_ipproto(int eproto)
+{
+	switch (eproto) {
+	case htons(ETH_P_IP):
+		return IPPROTO_IP;
+	case htons(ETH_P_IPV6):
+		return IPPROTO_IPV6;
+	default:
+		return -1;
+	}
+}
+
 #ifdef CONFIG_BUG
 void netdev_rx_csum_fault(struct net_device *dev);
 #else