netbuf.h

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#ifndef _NET_NETBUF_H
#define _NET_NETBUF_H
 
#include <core/system.h>
#include <core/panic.h>
 
struct netif;

struct netbuf {
    struct netbuf *next;    /* the next one in a queue, or on the free list */
    struct netif *netif;    /* the interface it came in on */
    uint8_t *data;
    size_t len;
 
    int loopback;           /* whether it's an IPv4 packet sent to ourselves */
 
    /* where a datagram came from (in a socket's queue) */
    uint32_t src_ip;
    uint16_t src_port;
 
    /* for a TCP segment that came before its turn: where its data goes,
     * and whether a FIN follows it */
    uint32_t seq;
    int fin;
 
    /* its page of memory, and the netbuf before it on the free list */
    paddr_t page;
    struct netbuf *free_prev;
};
 
/* A netbuf's size, and the room kept before the data for the headers
 * that the layers below add. */
#define NETBUF_SIZE     2048
#define NETBUF_HEADROOM 128
 
/* The end of a netbuf's room. */
#define NETBUF_END(nb)  ((uint8_t *) (nb) + NETBUF_SIZE)
 
/* Allocates a netbuf, or frees one. */
struct netbuf *netbuf_alloc(void);
void netbuf_free(struct netbuf *nb);

static inline void *netbuf_push(struct netbuf *nb, size_t size)
{
    if (nb->data - size < (uint8_t *) (nb + 1))
        panic("netbuf: no room for a header");
 
    nb->data -= size;
    nb->len  += size;
    return nb->data;
}

static inline void *netbuf_pull(struct netbuf *nb, size_t size)
{
    if (nb->len < size)
        return NULL;
 
    void *header = nb->data;
    nb->data += size;
    nb->len  -= size;
    return header;
}

static inline void *netbuf_put(struct netbuf *nb, size_t size)
{
    if (nb->data + nb->len + size > NETBUF_END(nb))
        return NULL;
 
    void *tail = nb->data + nb->len;
    nb->len += size;
    return tail;
}
 
#endif /* ! _NET_NETBUF_H */