build_skb(9) [centos man page]

BUILD_SKB(9)							 Linux Networking						      BUILD_SKB(9)

NAME

       build_skb - build a network buffer

SYNOPSIS

       struct sk_buff * build_skb(void * data, unsigned int frag_size);

ARGUMENTS

       data
	   data buffer provided by caller

       frag_size
	   size of fragment, or 0 if head was kmalloced

DESCRIPTION

       Allocate a new sk_buff. Caller provides space holding head and skb_shared_info.	data must have been allocated by kmalloc The return is the
       new skb buffer. On a failure the return is NULL, and data is not freed.

NOTES

       Before IO, driver allocates only data buffer where NIC put incoming frame Driver should add room at head (NET_SKB_PAD) and MUST add room at
       tail (SKB_DATA_ALIGN(skb_shared_info)) After IO, driver calls build_skb, to allocate sk_buff and populate it before giving packet to stack.
       RX rings only contains data buffers, not full skbs.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							      BUILD_SKB(9)

STRUCT 
SK_BUFF(9)						 Linux Networking						 STRUCT SK_BUFF(9)

NAME

       struct_sk_buff - socket buffer

SYNOPSIS

       struct sk_buff {
	 struct sk_buff * next;
	 struct sk_buff * prev;
	 ktime_t tstamp;
	 struct sock * sk;
	 struct net_device * dev;
	 char cb[48];
	 unsigned long _skb_dst;
       #ifdef CONFIG_XFRM
	 struct sec_path * sp;
       #endif
	 unsigned int len;
	 unsigned int data_len;
	 __u16 mac_len;
	 __u16 hdr_len;
	 union {unnamed_union};
	 __u16 vlan_tci;
	 sk_buff_data_t transport_header;
	 sk_buff_data_t network_header;
	 sk_buff_data_t mac_header;
	 sk_buff_data_t tail;
	 sk_buff_data_t end;
	 unsigned char * head;
	 unsigned char * data;
	 unsigned int truesize;
	 atomic_t users;
       };

MEMBERS

       next
	   Next buffer in list

       prev
	   Previous buffer in list

       tstamp
	   Time we arrived

       sk
	   Socket we are owned by

       dev
	   Device we arrived on/are leaving by

       cb[48]
	   Control buffer. Free for use by every layer. Put private vars here

       _skb_dst
	   destination entry

       sp
	   the security path, used for xfrm

       len
	   Length of actual data

       data_len
	   Data length

       mac_len
	   Length of link layer header

       hdr_len
	   writable header length of cloned skb

       {unnamed_union}
	   anonymous

       vlan_tci
	   vlan tag control information

       transport_header
	   Transport layer header

       network_header
	   Network layer header

       mac_header
	   Link layer header

       tail
	   Tail pointer

       end
	   End pointer

       head
	   Head of buffer

       data
	   Data head pointer

       truesize
	   Buffer size

       users
	   User count - see {datagram,tcp}.c

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010							 STRUCT SK_BUFF(9)