os_mbuf_append

int os_mbuf_append(struct os_mbuf *om, const void *data,  uint16_t len)

Appends a data buffer of length len to the end of an mbuf chain, adjusting packet length if om is a packet header mbuf. If not enough trailing space exists at the end of the mbuf chain, mbufs are allocated to hold the data.

Arguments

Arguments	Description
om	Pointer to mbuf. Can be head of a chain of mbufs, a single mbuf or a packet header mbuf
data	Pointer to data buffer to copy from
len	Number of bytes to copy from data buffer to the end of the mbuf

Returned values

0: success
OS_ENOMEM: Could not allocate enough mbufs to hold data.
OS_EINVAL: om was NULL on entry.

Notes

If not enough mbufs were available the packet header length of the mbuf may get adjusted even though the entire data buffer was not appended to the end of the mbuf.

If any mbufs are allocated, they are allocated from the same pool as om

Example

    int rc;
    uint16_t pktlen;
	struct os_mbuf *om;
	struct my_data_struct my_data;
	
    /* Get initial packet length */
    pktlen = OS_MBUF_PKTLEN(om);

	/* Append "my_data" to end of mbuf, freeing mbuf if unable to append all the data */
    rc = os_mbuf_append(om, &my_data, sizeof(struct my_pkt_header));
    if (rc) {
        os_mbuf_free_chain(om);
    }
    pktlen += sizeof(struct my_pkt_header);

    /* New packet length should be initial packet length plus length of "my_data" */
	assert(pktlen == OS_MBUF_PKTLEN(om));