sk_buff

基于linux-5.14.14版本

1. sk_buff结构体

struct sk_buff {
	union {
		struct {
			struct sk_buff		*next; //双向链表头指针
			struct sk_buff		*prev; //双向链表尾指针
			union {
				struct net_device	*dev; //网络结构体
				unsigned long		dev_scratch;
			};
		};
		struct rb_node		rbnode;
		struct list_head	list;
	};
	union {
		struct sock		*sk;
		int			ip_defrag_offset;
	};
	union {
		ktime_t		tstamp;
		u64		skb_mstamp_ns; 
	};
	char			cb[48] __aligned(8);
	union {
		struct {
			unsigned long	_skb_refdst;
			void		(*destructor)(struct sk_buff *skb);
		};
		struct list_head	tcp_tsorted_anchor;
#ifdef CONFIG_NET_SOCK_MSG
		unsigned long		_sk_redir;
#endif
	};

#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	unsigned long		 _nfct;
#endif
	unsigned int		len, data_len;
	__u16			mac_len, hdr_len;
	__u16			queue_mapping;

#ifdef __BIG_ENDIAN_BITFIELD
#define CLONED_MASK	(1 << 7)
#else
#define CLONED_MASK	1
#endif
#define CLONED_OFFSET()		offsetof(struct sk_buff, __cloned_offset)

	__u8			__cloned_offset[0];
	__u8			cloned:1,
				nohdr:1,
				fclone:2,
				peeked:1,
				head_frag:1,
				pfmemalloc:1,
				pp_recycle:1;
#ifdef CONFIG_SKB_EXTENSIONS
	__u8			active_extensions;
#endif
	__u32			headers_start[0];
#ifdef __BIG_ENDIAN_BITFIELD
#define PKT_TYPE_MAX	(7 << 5)
#else
#define PKT_TYPE_MAX	7
#endif
#define PKT_TYPE_OFFSET()	offsetof(struct sk_buff, __pkt_type_offset)

	__u8			__pkt_type_offset[0];
	__u8			pkt_type:3;
	__u8			ignore_df:1;
	__u8			nf_trace:1;
	__u8			ip_summed:2;
	__u8			ooo_okay:1;

	__u8			l4_hash:1;
	__u8			sw_hash:1;
	__u8			wifi_acked_valid:1;
	__u8			wifi_acked:1;
	__u8			no_fcs:1;
	__u8			encapsulation:1;
	__u8			encap_hdr_csum:1;
	__u8			csum_valid:1;

#ifdef __BIG_ENDIAN_BITFIELD
#define PKT_VLAN_PRESENT_BIT	7
#else
#define PKT_VLAN_PRESENT_BIT	0
#endif
#define PKT_VLAN_PRESENT_OFFSET()	offsetof(struct sk_buff, __pkt_vlan_present_offset)
	__u8			__pkt_vlan_present_offset[0];
	__u8			vlan_present:1;
	__u8			csum_complete_sw:1;
	__u8			csum_level:2;
	__u8			csum_not_inet:1;
	__u8			dst_pending_confirm:1;
#ifdef CONFIG_IPV6_NDISC_NODETYPE
	__u8			ndisc_nodetype:2;
#endif

	__u8			ipvs_property:1;
	__u8			inner_protocol_type:1;
	__u8			remcsum_offload:1;
#ifdef CONFIG_NET_SWITCHDEV
	__u8			offload_fwd_mark:1;
	__u8			offload_l3_fwd_mark:1;
#endif
#ifdef CONFIG_NET_CLS_ACT
	__u8			tc_skip_classify:1;
	__u8			tc_at_ingress:1;
#endif
#ifdef CONFIG_NET_REDIRECT
	__u8			redirected:1;
	__u8			from_ingress:1;
#endif
#ifdef CONFIG_TLS_DEVICE
	__u8			decrypted:1;
#endif

#ifdef CONFIG_NET_SCHED
	__u16			tc_index;
#endif

	union {
		__wsum		csum;
		struct {
			__u16	csum_start;
			__u16	csum_offset;
		};
	};
	__u32			priority;
	int			    skb_iif;
	__u32			hash;
	__be16			vlan_proto;
	__u16			vlan_tci;
#if defined(CONFIG_NET_RX_BUSY_POLL) || defined(CONFIG_XPS)
	union {
		unsigned int	napi_id;
		unsigned int	sender_cpu;
	};
#endif
#ifdef CONFIG_NETWORK_SECMARK
	__u32		secmark;
#endif

	union {
		__u32		mark;
		__u32		reserved_tailroom;
	};

	union {
		__be16		inner_protocol;
		__u8		inner_ipproto;
	};
	
	__u16			inner_transport_header;
	__u16			inner_network_header;
	__u16			inner_mac_header;

	__be16			protocol;
	__u16			transport_header;
	__u16			network_header;
	__u16			mac_header;

#ifdef CONFIG_KCOV
	u64			kcov_handle;
#endif
	__u32			headers_end[0];
	sk_buff_data_t		tail;
	sk_buff_data_t		end;
	unsigned char		*head,*data;
	unsigned int		truesize;
	refcount_t		users;

#ifdef CONFIG_SKB_EXTENSIONS
	struct skb_ext		*extensions;
#endif
};