// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/if_vlan.h>
#include <net/ip.h>
#include <net/tso.h>
#include <linux/unaligned.h>

void tso_build_hdr(const struct sk_buff *skb, char *hdr, struct tso_t *tso,
                   int size, bool is_last)
{
        int hdr_len = skb_transport_offset(skb) + tso->tlen;
        int mac_hdr_len = skb_network_offset(skb);

        memcpy(hdr, skb->data, hdr_len);
        if (!tso->ipv6) {
                struct iphdr *iph = (void *)(hdr + mac_hdr_len);

                iph->id = htons(tso->ip_id);
                iph->tot_len = htons(size + hdr_len - mac_hdr_len);
                tso->ip_id++;
        } else {
                struct ipv6hdr *iph = (void *)(hdr + mac_hdr_len);

                iph->payload_len = htons(size + tso->tlen);
        }
        hdr += skb_transport_offset(skb);
        if (tso->tlen != sizeof(struct udphdr)) {
                struct tcphdr *tcph = (struct tcphdr *)hdr;

                put_unaligned_be32(tso->tcp_seq, &tcph->seq);

                if (!is_last) {
                        /* Clear all special flags for not last packet */
                        tcph->psh = 0;
                        tcph->fin = 0;
                        tcph->rst = 0;
                }
        } else {
                struct udphdr *uh = (struct udphdr *)hdr;

                uh->len = htons(sizeof(*uh) + size);
        }
}
EXPORT_SYMBOL(tso_build_hdr);

void tso_build_data(const struct sk_buff *skb, struct tso_t *tso, int size)
{
        tso->tcp_seq += size; /* not worth avoiding this operation for UDP */
        tso->size -= size;
        tso->data += size;

        if ((tso->size == 0) &&
            (tso->next_frag_idx < skb_shinfo(skb)->nr_frags)) {
                skb_frag_t *frag = &skb_shinfo(skb)->frags[tso->next_frag_idx];

                /* Move to next segment */
                tso->size = skb_frag_size(frag);
                tso->data = skb_frag_address(frag);
                tso->next_frag_idx++;
        }
}
EXPORT_SYMBOL(tso_build_data);

int tso_start(struct sk_buff *skb, struct tso_t *tso)
{
        int tlen = skb_is_gso_tcp(skb) ? tcp_hdrlen(skb) : sizeof(struct udphdr);
        int hdr_len = skb_transport_offset(skb) + tlen;

        tso->tlen = tlen;
        tso->ip_id = ntohs(ip_hdr(skb)->id);
        tso->tcp_seq = (tlen != sizeof(struct udphdr)) ? ntohl(tcp_hdr(skb)->seq) : 0;
        tso->next_frag_idx = 0;
        tso->ipv6 = vlan_get_protocol(skb) == htons(ETH_P_IPV6);

        /* Build first data */
        tso->size = skb_headlen(skb) - hdr_len;
        tso->data = skb->data + hdr_len;
        if ((tso->size == 0) &&
            (tso->next_frag_idx < skb_shinfo(skb)->nr_frags)) {
                skb_frag_t *frag = &skb_shinfo(skb)->frags[tso->next_frag_idx];

                /* Move to next segment */
                tso->size = skb_frag_size(frag);
                tso->data = skb_frag_address(frag);
                tso->next_frag_idx++;
        }
        return hdr_len;
}
EXPORT_SYMBOL(tso_start);