kkumar-fk

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <strings.h>
#include <sys/wait.h>
#include <netdb.h>

void create_children(int nprocs, int parent_pid)
{
	while (nprocs-- > 0) {

kkumar-fk

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <netdb.h>

void create_children(int nprocs, int parent_pid)
{
	while (nprocs-- > 0) {
		if (getpid() == parent_pid && fork() < 0)

kkumar-fk

# Server is listening on port #45000
$ ss -tan | grep :45000
LISTEN   0     1        10.20.1.1:45000        *:*

# A client connects to the server using it's source port 54762. A new
# socket is created and is seen in ESTABLISHED state, along with the
# earlier LISTEN socket.
$ ss -tan | grep :45000
LISTEN     0     1      10.20.1.1:45000        *:*
ESTAB      0     0      10.20.1.1:45000        10.20.1.100:54762

kkumar-fk

#define LHTABLE_SIZE 32  /* Yes, really, this is all you need */

struct inet_hashinfo {
    /* Hash table for fully established sockets */
    struct inet_ehash_bucket *ehash;
    /* Hash table for LISTEN sockets */
    struct inet_listen_hashbucket listening_hash[LHTABLE_SIZE];
};

struct inet_hashinfo tcp_hashinfo;

kkumar-fk

struct sock *__inet_lookup_skb(tcp_hashinfo, skb, src_port, dst_port)
{
    /* Get the IPv4 header to know the source and destination IP's */
    const struct iphdr *iph = ip_hdr(skb);

    /*
     * Look up the incoming skb in tcp_hashinfo using the
     * [ Source-IP:Port, Destination-IP:Port ] tuple.
     */
    return __inet_lookup(tcp_hashinfo, skb, iph->saddr, src_port, iph->daddr, dst_port);

kkumar-fk

struct sock *__inet_lookup(tcp_hashinfo, skb, src_addr, src_port, dst_addr, dst_port)
{
    /* Convert dest_port# from network to host byte order */
    u16 hnum = ntohs(dst_port);

    /* First look for an established socket ... */
    sk = __inet_lookup_established(tcp_hashinfo, src_addr, src_port, dst_addr, hnum);
    if (sk)
        return sk;

kkumar-fk

struct sock *__inet_lookup_listener(tcp_hashinfo, skb, src_addr, src_port, dst_addr, dst_port)
{
	/*
	 * Use the destination port# to calculate a hash table slot# of the listen socket.
	 * inet_lhashfn() returns a number between 0 and INET_LHTABLE_SIZE-1 (both
	 * inclusive).
	 */
	unsigned int hash = inet_lhashfn(dst_port);

	/* Use this hash slot# to index the global LISTEN hash table */

kkumar-fk

struct sock *reuseport_select_sock(struct sock *sk, unsigned int phash)
{
    /* Get control block of sockets in this SO_REUSEPORT group */
    struct sock_reuseport *reuse = sk->sk_reuseport_cb;

    /* Get count of sockets in the group */
    int num_socks = reuse->num_socks;

    /* Calculate value between 0 and 'num_socks-1' (both inclusive) */
    unsigned int index = reciprocal_scale(phash, num_socks);

kkumar-fk

struct sock_reuseport {
    u16		max_socks; /* Allocated size of socks[] array */
    u16		num_socks; /* #Elements in socks[] */
    struct sock	*socks[0]; /* All sockets added to this group */
};

kkumar-fk

static int inet_reuseport_add_sock(struct sock *new_sk)
{
    /* First check if another identical LISTEN socket, prev_sk,
     * exists. ... Then do the following:
     */
    if (prev_sk) {
        /*
         * Not the first listener - do the following:
         *	- Grow prev_sk->sk_reuseport_cb structure if required.
         *	- Save new_sk socket pointer in prev_sk's socks[].