Function

mbuf_allocpacket

Declaration

errno_t mbuf_allocpacket(mbuf_how_t how, size_t packetlen, unsigned int *maxchunks, mbuf_t *mbuf);

Parameters

how

Blocking or non-blocking

packetlen

The total length of the packet mbuf to be allocated. The length must be greater than zero.

maxchunks

An input/output pointer to the maximum number of mbufs segments making up the chain. On input, if maxchunks is NULL, or the value pointed to by maxchunks is zero, the packet will be made up of as few or as many buffer segments as necessary to fit the length. The allocation will fail with ENOBUFS if the number of segments requested is too small and the sum of the maximum size of each individual segment is less than the packet length. On output, if the allocation succeed and maxchunks is non-NULL, it will point to the actual number of segments allocated. Additional notes for packetlen greater than 4096 bytes: the caller may pass a non-NULL maxchunks and initialize it with zero such that upon success, it can find out whether or not the system configuration allows for larger than 4096 bytes cluster allocations, by checking on the value pointed to by maxchunks. E.g. a request for 9018 bytes may result in 1 chunk when jumbo clusters are available, or 3 chunks otherwise.

Upon

success, *mbuf will be a reference to the new mbuf.

Return Value

Returns 0 upon success or the following error code: EINVAL - Invalid parameter ENOMEM - Not enough memory available ENOBUFS - Buffers not big enough for the maximum number of chunks requested

Discussion

Allocate an mbuf chain to store a single packet of the requested length. According to the requested length, a chain of mbufs will be created. The mbuf type will be set to MBUF_TYPE_DATA. The caller may specify the maximum number of buffer.