To ease changes to underlying mbuf structure and the mbuf allocator, reduce

the knowledge of mbuf layout, and in particular constants such as M_EXT,
MLEN, MHLEN, and so on, in mbuf consumers by unifying various alignment
utility functions (M_ALIGN(), MH_ALIGN(), MEXT_ALIGN() in a single
M_ALIGN() macro, implemented by a now-inlined m_align() function:

- Move m_align() from uipc_mbuf.c to mbuf.h; mark as __inline.
- Reimplement M_ALIGN(), MH_ALIGN(), and MEXT_ALIGN() using m_align().
- Update consumers around the tree to simply use M_ALIGN().

This change eliminates a number of cases where mbuf consumers must be aware
of whether or not mbufs returned by the allocator use external storage, but
also assumptions about the size of the returned mbuf. This will make it
easier to introduce changes in how we use external storage, as well as
features such as variable-size mbufs.

Differential Revision:	https://reviews.freebsd.org/D1436
Reviewed by:	glebius, trasz, gnn, bz
Sponsored by:	EMC / Isilon Storage Division

5 files changed, 9 insertions, 13 deletions

diff --git a/sys/netinet/if_ether.c b/sys/netinet/if_ether.c
index f1d0656..840598d 100644
--- a/sys/netinet/if_ether.c
+++ b/sys/netinet/if_ether.c
@@ -261,7 +261,7 @@ arprequest(struct ifnet *ifp, const struct in_addr *sip,
 	m->m_len = sizeof(*ah) + 2 * sizeof(struct in_addr) +
 		2 * ifp->if_addrlen;
 	m->m_pkthdr.len = m->m_len;
-	MH_ALIGN(m, m->m_len);
+	M_ALIGN(m, m->m_len);
 	ah = mtod(m, struct arphdr *);
 	bzero((caddr_t)ah, m->m_len);
 #ifdef MAC
diff --git a/sys/netinet/igmp.c b/sys/netinet/igmp.c
index 210b24f..4ed25a5 100644
--- a/sys/netinet/igmp.c
+++ b/sys/netinet/igmp.c
@@ -2212,7 +2212,7 @@ igmp_v1v2_queue_report(struct in_multi *inm, const int type)
 	m = m_gethdr(M_NOWAIT, MT_DATA);
 	if (m == NULL)
 		return (ENOMEM);
-	MH_ALIGN(m, sizeof(struct ip) + sizeof(struct igmp));
+	M_ALIGN(m, sizeof(struct ip) + sizeof(struct igmp));
 
 	m->m_pkthdr.len = sizeof(struct ip) + sizeof(struct igmp);
 
@@ -2793,7 +2793,7 @@ igmp_v3_enqueue_group_record(struct ifqueue *ifq, struct in_multi *inm,
 		if (m == NULL) {
 			m = m_gethdr(M_NOWAIT, MT_DATA);
 			if (m)
-				MH_ALIGN(m, IGMP_LEADINGSPACE);
+				M_ALIGN(m, IGMP_LEADINGSPACE);
 		}
 		if (m == NULL)
 			return (-ENOMEM);
@@ -2917,7 +2917,7 @@ igmp_v3_enqueue_group_record(struct ifqueue *ifq, struct in_multi *inm,
 		if (m == NULL) {
 			m = m_gethdr(M_NOWAIT, MT_DATA);
 			if (m)
-				MH_ALIGN(m, IGMP_LEADINGSPACE);
+				M_ALIGN(m, IGMP_LEADINGSPACE);
 		}
 		if (m == NULL)
 			return (-ENOMEM);
@@ -3073,7 +3073,7 @@ igmp_v3_enqueue_filter_change(struct ifqueue *ifq, struct in_multi *inm)
 				if (m == NULL) {
 					m = m_gethdr(M_NOWAIT, MT_DATA);
 					if (m)
-						MH_ALIGN(m, IGMP_LEADINGSPACE);
+						M_ALIGN(m, IGMP_LEADINGSPACE);
 				}
 				if (m == NULL) {
 					CTR1(KTR_IGMPV3,
diff --git a/sys/netinet/ip_carp.c b/sys/netinet/ip_carp.c
index 7208764..9786273 100644
--- a/sys/netinet/ip_carp.c
+++ b/sys/netinet/ip_carp.c
@@ -840,7 +840,7 @@ carp_send_ad_locked(struct carp_softc *sc)
 		m->m_pkthdr.len = len;
 		m->m_pkthdr.rcvif = NULL;
 		m->m_len = len;
-		MH_ALIGN(m, m->m_len);
+		M_ALIGN(m, m->m_len);
 		m->m_flags |= M_MCAST;
 		ip = mtod(m, struct ip *);
 		ip->ip_v = IPVERSION;
@@ -892,7 +892,7 @@ carp_send_ad_locked(struct carp_softc *sc)
 		m->m_pkthdr.len = len;
 		m->m_pkthdr.rcvif = NULL;
 		m->m_len = len;
-		MH_ALIGN(m, m->m_len);
+		M_ALIGN(m, m->m_len);
 		m->m_flags |= M_MCAST;
 		ip6 = mtod(m, struct ip6_hdr *);
 		bzero(ip6, sizeof(*ip6));
diff --git a/sys/netinet/sctp_os_bsd.h b/sys/netinet/sctp_os_bsd.h
index 9d54663..53427ce 100644
--- a/sys/netinet/sctp_os_bsd.h
+++ b/sys/netinet/sctp_os_bsd.h
@@ -304,11 +304,7 @@ typedef struct callout sctp_os_timer_t;
 #define SCTP_BUF_RECVIF(m) (m->m_pkthdr.rcvif)
 #define SCTP_BUF_PREPEND	M_PREPEND
 
-#define SCTP_ALIGN_TO_END(m, len) if(m->m_flags & M_PKTHDR) { \
-                                     MH_ALIGN(m, len); \
-                                  } else if ((m->m_flags & M_EXT) == 0) { \
-                                     M_ALIGN(m, len); \
-                                  }
+#define SCTP_ALIGN_TO_END(m, len) M_ALIGN(m, len)
 
 /* We make it so if you have up to 4 threads
  * writing based on the default size of
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 160fada..eb4cb47 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -1007,7 +1007,7 @@ send:
 #ifdef INET6
 		if (isipv6 && (MHLEN < hdrlen + max_linkhdr) &&
 		    MHLEN >= hdrlen) {
-			MH_ALIGN(m, hdrlen);
+			M_ALIGN(m, hdrlen);
 		} else
 #endif
 		m->m_data += max_linkhdr;