---
- branch: MAIN
  date: Wed Apr 12 06:48:08 UTC 2023
  files:
  - new: '1.251'
    old: '1.250'
    path: src/sys/kern/uipc_mbuf.c
    pathrev: src/sys/kern/uipc_mbuf.c@1.251
    type: modified
  - new: '1.238'
    old: '1.237'
    path: src/sys/sys/mbuf.h
    pathrev: src/sys/sys/mbuf.h@1.238
    type: modified
  id: 20230412T064808Z.1a49a8182be7438eef3452584b4cf88f5c84fdb3
  log: |
    mbuf(9): New m_get_n, m_gethdr_n.

    m_get_n(how, type, alignbytes, nbytes) returns an mbuf with no packet
    header having space for nbytes, with an internal buffer pointer
    aligned by alignbytes (typically ETHER_ALIGN or similar, if not
    zero).

    m_gethdr_n(how, type, alignbytes, nbytes) does the same but for an
    mbuf with a packet header.

    These return NULL on failure, which can happen either:
    (a) because how is M_DONTWAIT and allocating memory would sleep, or
    (b) because alignbytes + nbytes > MCLBYTES.

    On exit, m_len is set to nbytes, as is m_pkthdr.len for m_gethdr_n.

    These should be used to systematically replace all calls to m_get,
    m_gethdr, MGET, MGETHDR, and m_getcl.  Most calls to m_clget and
    MCLGET will probably evaporate as a consequence.

    Proposed on tech-net last year:
    https://mail-index.netbsd.org/tech-net/2022/07/16/msg008285.html
  module: src
  subject: 'CVS commit: src/sys'
  unixtime: '1681282088'
  user: riastradh