centos man page for __skb_recv_datagram

__SKB_RECV_DATAGRAM(9)						 Linux Networking					    __SKB_RECV_DATAGRAM(9)

NAME
       __skb_recv_datagram - Receive a datagram skbuff

SYNOPSIS
       struct sk_buff * __skb_recv_datagram(struct sock * sk, unsigned int flags, int * peeked, int * off, int * err);

ARGUMENTS
       sk
	   socket

       flags
	   MSG_ flags

       peeked
	   returns non-zero if this packet has been seen before

       off
	   an offset in bytes to peek skb from. Returns an offset within an skb where data actually starts

       err
	   error code returned

DESCRIPTION
       Get a datagram skbuff, understands the peeking, nonblocking wakeups and possible races. This replaces identical code in packet, raw and
       udp, as well as the IPX AX.25 and Appletalk. It also finally fixes the long standing peek and read race for datagram sockets. If you alter
       this routine remember it must be re-entrant.

       This function will lock the socket if a skb is returned, so the caller needs to unlock the socket in that case (usually by calling
       skb_free_datagram)

       * It does not lock socket since today. This function is * free of race conditions. This measure should/can improve * significantly datagram
       socket latencies at high loads, * when data copying to user space takes lots of time. * (BTW I've just killed the last cli in
       IP/IPv6/core/netlink/packet * 8) Great win.) * --ANK (980729)

       The order of the tests when we find no data waiting are specified quite explicitly by POSIX 1003.1g, don't change them without having the
       standard around please.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014						    __SKB_RECV_DATAGRAM(9)