root/include/net/netfilter/nf_queue.h

DEFINITIONS

1. init_hashrandom
2. hash_v4
3. hash_v6
4. nfqueue_hash

#ifndef _NF_QUEUE_H
#define _NF_QUEUE_H

#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/jhash.h>

/* Each queued (to userspace) skbuff has one of these. */
struct nf_queue_entry {
        struct list_head        list;
        struct sk_buff          *skb;
        unsigned int            id;

        struct nf_hook_ops      *elem;
        u_int8_t                pf;
        u16                     size; /* sizeof(entry) + saved route keys */
        unsigned int            hook;
        struct net_device       *indev;
        struct net_device       *outdev;
        int                     (*okfn)(struct sk_buff *);

        /* extra space to store route keys */
};

#define nf_queue_entry_reroute(x) ((void *)x + sizeof(struct nf_queue_entry))

/* Packet queuing */
struct nf_queue_handler {
        int                     (*outfn)(struct nf_queue_entry *entry,
                                         unsigned int queuenum);
};

void nf_register_queue_handler(const struct nf_queue_handler *qh);
void nf_unregister_queue_handler(void);
void nf_reinject(struct nf_queue_entry *entry, unsigned int verdict);

bool nf_queue_entry_get_refs(struct nf_queue_entry *entry);
void nf_queue_entry_release_refs(struct nf_queue_entry *entry);

static inline void init_hashrandom(u32 *jhash_initval)
{
        while (*jhash_initval == 0)
                *jhash_initval = prandom_u32();
}

static inline u32 hash_v4(const struct sk_buff *skb, u32 jhash_initval)
{
        const struct iphdr *iph = ip_hdr(skb);

        /* packets in either direction go into same queue */
        if ((__force u32)iph->saddr < (__force u32)iph->daddr)
                return jhash_3words((__force u32)iph->saddr,
                        (__force u32)iph->daddr, iph->protocol, jhash_initval);

        return jhash_3words((__force u32)iph->daddr,
                        (__force u32)iph->saddr, iph->protocol, jhash_initval);
}

#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
static inline u32 hash_v6(const struct sk_buff *skb, u32 jhash_initval)
{
        const struct ipv6hdr *ip6h = ipv6_hdr(skb);
        u32 a, b, c;

        if ((__force u32)ip6h->saddr.s6_addr32[3] <
            (__force u32)ip6h->daddr.s6_addr32[3]) {
                a = (__force u32) ip6h->saddr.s6_addr32[3];
                b = (__force u32) ip6h->daddr.s6_addr32[3];
        } else {
                b = (__force u32) ip6h->saddr.s6_addr32[3];
                a = (__force u32) ip6h->daddr.s6_addr32[3];
        }

        if ((__force u32)ip6h->saddr.s6_addr32[1] <
            (__force u32)ip6h->daddr.s6_addr32[1])
                c = (__force u32) ip6h->saddr.s6_addr32[1];
        else
                c = (__force u32) ip6h->daddr.s6_addr32[1];

        return jhash_3words(a, b, c, jhash_initval);
}
#endif

static inline u32
nfqueue_hash(const struct sk_buff *skb, u16 queue, u16 queues_total, u8 family,
             u32 jhash_initval)
{
        if (family == NFPROTO_IPV4)
                queue += ((u64) hash_v4(skb, jhash_initval) * queues_total) >> 32;
#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
        else if (family == NFPROTO_IPV6)
                queue += ((u64) hash_v6(skb, jhash_initval) * queues_total) >> 32;
#endif

        return queue;
}

#endif /* _NF_QUEUE_H */