mbuf initialization macros

[Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>]

Hi,

I found some functions(e.g. _pf_mtap2()@sys/net/bpf.c) use mbuf allocated
on stack instead of allocated by m_get(). Furthermore, the functions
initialize mbuf incompletely. It might cause problems when struct mbuf
fields is modified.

I think mbuf initialization macros is required to prevent these potential
problems. That is, the following patch is required.

====================
diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index f2056da..a8426b7 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -583,14 +583,10 @@ m_get(int nowait, int type)
                return NULL;
 
        mbstat_type_add(type, 1);
+
+       M_HDR_INIT(m);
        mowner_init(m, type);
-       m->m_ext_ref = m;
        m->m_type = type;
-       m->m_len = 0;
-       m->m_next = NULL;
-       m->m_nextpkt = NULL;
-       m->m_data = m->m_dat;
-       m->m_flags = 0;
 
        return m;
 }
@@ -606,11 +602,8 @@ m_gethdr(int nowait, int type)
 
        m->m_data = m->m_pktdat;
        m->m_flags = M_PKTHDR;
-       m->m_pkthdr.rcvif = NULL;
-       m->m_pkthdr.len = 0;
-       m->m_pkthdr.csum_flags = 0;
-       m->m_pkthdr.csum_data = 0;
-       SLIST_INIT(&m->m_pkthdr.tags);
+
+       M_PKTHDR_INIT(m);
 
        return m;
 }
diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index 75f4d64..6882241 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -179,6 +179,24 @@ struct     pkthdr {
        u_int           segsz;                  /* segment size */
 };
 
+#define M_HDR_INIT(_m) do {                                            \
+               (_m)->m_ext_ref = (_m);                                 \
+               (_m)->m_type = MT_DATA;                                 \
+               (_m)->m_len = 0;                                        \
+               (_m)->m_next = NULL;                                    \
+               (_m)->m_nextpkt = NULL;                                 \
+               (_m)->m_data = (_m)->m_dat;                             \
+               (_m)->m_flags = 0;                                      \
+       } while(0)
+
+#define M_PKTHDR_INIT(_m) do {                                         \
+               (_m)->m_pkthdr.rcvif = NULL;                            \
+               (_m)->m_pkthdr.len = 0;                                 \
+               (_m)->m_pkthdr.csum_flags = 0;                          \
+               (_m)->m_pkthdr.csum_data = 0;                           \
+               SLIST_INIT(&(_m)->m_pkthdr.tags);                       \
+       } while(0)
+
 /*
  * Note: These bits are carefully arrange so that the compiler can have
  * a prayer of generating a jump table.
====================

Could you comment this patch?
I will commit this patch after a few days or a few weeks if there is
no objection.
# And then, I will apply the macros to mbufs allocated on stack bit by bit.


Thanks,

-- 
//////////////////////////////////////////////////////////////////////
Internet Initiative Japan Inc.

Device Engineering Section,
IoT Platform Development Department,
Network Division,
Technology Unit

Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>