From 64a93525ad939b18b84b0c5fad5e23dc92a84a16 Mon Sep 17 00:00:00 2001
From: bluhm <bluhm@openbsd.org>
Date: Thu, 5 Sep 2024 08:52:27 +0000
Subject: [PATCH] In ddb(4) print mbuf chain and packet list.

For debugging hardware offloading, DMA requirements, bounce buffers,
and performance optimizations, knowing the memory layout of mbuf
content helps.
Implement /c and /p modifiers in ddb show mbuf.  It traverses the
pointer m_next for mbuf chain or m_nextpkt for packet list.  Show
mbuf type, data offset, mbuf length, packet length, cluster size,
and total number of elements, length and size.

OK claudio@ mvs@
---
 share/man/man4/ddb.4   | 17 ++++++++--
 sys/ddb/db_command.c   | 12 +++++--
 sys/ddb/db_interface.h |  4 ++-
 sys/kern/uipc_mbuf.c   | 76 +++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 102 insertions(+), 7 deletions(-)

diff --git a/share/man/man4/ddb.4 b/share/man/man4/ddb.4
index 690405108f7..6ca75c4d593 100644
--- a/share/man/man4/ddb.4
+++ b/share/man/man4/ddb.4
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: ddb.4,v 1.107 2024/02/05 21:33:00 jmc Exp $
+.\"	$OpenBSD: ddb.4,v 1.108 2024/09/05 08:52:27 bluhm Exp $
 .\"	$NetBSD: ddb.4,v 1.5 1994/11/30 16:22:09 jtc Exp $
 .\"
 .\" Mach Operating System
@@ -25,7 +25,7 @@
 .\" any improvements or extensions that they make and grant Carnegie Mellon
 .\" the rights to redistribute these changes.
 .\"
-.Dd $Mdocdate: February 5 2024 $
+.Dd $Mdocdate: September 5 2024 $
 .Dt DDB 4
 .Os
 .Sh NAME
@@ -658,7 +658,11 @@ If the
 .Cm /f
 modifier is specified, the complete map is printed.
 .\" --------------------
-.It Ic show mbuf Ar addr
+.It Xo
+.Ic show mbuf
+.Op Cm /cp
+.Ar addr
+.Xc
 Prints the
 .Vt struct mbuf
 header at
@@ -668,6 +672,13 @@ Depending on the mbuf flags
 and
 .Vt struct m_ext
 are printed as well.
+If the
+.Cm /c
+modifier is specified, print the mbuf chain linked with the m_next
+pointer.
+.Cm /p
+does the same using m_nextpkt.
+Both can be combined.
 .\" --------------------
 .It Xo
 .Ic show mount
diff --git a/sys/ddb/db_command.c b/sys/ddb/db_command.c
index 562053d112a..1e129c2e03c 100644
--- a/sys/ddb/db_command.c
+++ b/sys/ddb/db_command.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_command.c,v 1.101 2024/05/13 01:15:50 jsg Exp $	*/
+/*	$OpenBSD: db_command.c,v 1.102 2024/09/05 08:52:27 bluhm Exp $	*/
 /*	$NetBSD: db_command.c,v 1.20 1996/03/30 22:30:05 christos Exp $	*/
 
 /*
@@ -340,7 +340,15 @@ db_malloc_print_cmd(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
 void
 db_mbuf_print_cmd(db_expr_t addr, int have_addr, db_expr_t count, char *modif)
 {
-	m_print((void *)addr, db_printf);
+	if ((modif[0] == 'c' && modif[1] == 'p') ||
+	    (modif[0] == 'p' && modif[1] == 'c'))
+		m_print_packet((void *)addr, 1, db_printf);
+	else if (modif[0] == 'c')
+		m_print_chain((void *)addr, 0, db_printf);
+	else if (modif[0] == 'p')
+		m_print_packet((void *)addr, 0, db_printf);
+	else
+		m_print((void *)addr, db_printf);
 }
 
 void
diff --git a/sys/ddb/db_interface.h b/sys/ddb/db_interface.h
index cccec9ed69c..bdde7ae345f 100644
--- a/sys/ddb/db_interface.h
+++ b/sys/ddb/db_interface.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.h,v 1.27 2024/02/03 18:51:58 beck Exp $	*/
+/*	$OpenBSD: db_interface.h,v 1.28 2024/09/05 08:52:27 bluhm Exp $	*/
 /*	$NetBSD: db_interface.h,v 1.1 1996/02/05 01:57:03 christos Exp $	*/
 
 /*
@@ -61,6 +61,8 @@ void db_show_all_pools(db_expr_t, int, db_expr_t, char *);
 
 /* kern/uipc_mbuf.c */
 void m_print(void *, int (*)(const char *, ...));
+void m_print_chain(void *, int, int (*)(const char *, ...));
+void m_print_packet(void *, int, int (*)(const char *, ...));
 
 /* kern/uipc_socket.c */
 void so_print(void *, int (*)(const char *, ...));
diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index db942bfd7d6..a0c0ebc9482 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_mbuf.c,v 1.291 2024/08/29 10:44:40 bluhm Exp $	*/
+/*	$OpenBSD: uipc_mbuf.c,v 1.292 2024/09/05 08:52:27 bluhm Exp $	*/
 /*	$NetBSD: uipc_mbuf.c,v 1.15.4.1 1996/06/13 17:11:44 cgd Exp $	*/
 
 /*
@@ -1533,6 +1533,80 @@ m_print(void *v,
 
 	}
 }
+
+const char *m_types[MT_NTYPES] = {
+	"fre",
+	"dat",
+	"hdr",
+	"nam",
+	"opt",
+	"ftb",
+	"ctl",
+	"oob",
+};
+
+void
+m_print_chain(void *v, int deep,
+    int (*pr)(const char *, ...) __attribute__((__format__(__kprintf__,1,2))))
+{
+	struct mbuf *m;
+	const char *indent = deep ? "++-" : "-+-";
+	size_t chain = 0, len = 0, size = 0;
+
+	for (m = v; m != NULL; m = m->m_next) {
+		const char *type;
+
+		chain++;
+		len += m->m_len;
+		size += M_SIZE(m);
+		type = (m->m_type >= 0 && m->m_type < MT_NTYPES) ?
+		    m_types[m->m_type] : "???";
+		(*pr)("%s mbuf %p, %s, off %zd, len %u", indent, m, type,
+		    m->m_data - M_DATABUF(m), m->m_len);
+		if (m->m_flags & M_PKTHDR)
+			(*pr)(", pktlen %d", m->m_pkthdr.len);
+		if (m->m_flags & M_EXT)
+			(*pr)(", clsize %u", m->m_ext.ext_size);
+		(*pr)("\n");
+		indent = deep ? "|+-" : " +-";
+	}
+	indent = deep ? "|\\-" : " \\-";
+	if (v != NULL) {
+		(*pr)("%s total chain %zu, len %zu, size %zu\n",
+		    indent, chain, len, size);
+	}
+}
+
+void
+m_print_packet(void *v, int deep,
+    int (*pr)(const char *, ...) __attribute__((__format__(__kprintf__,1,2))))
+{
+	struct mbuf *m, *n;
+	const char *indent = "+--";
+	size_t pkts = 0;
+
+	for (m = v; m != NULL; m = m->m_nextpkt) {
+		size_t chain = 0, len = 0, size = 0;
+
+		pkts++;
+		if (deep) {
+			m_print_chain(m, deep, pr);
+			continue;
+		}
+		for (n = m; n != NULL; n = n->m_next) {
+			chain++;
+			len += n->m_len;
+			size += M_SIZE(n);
+		}
+		(*pr)("%s mbuf %p, chain %zu", indent, m, chain);
+		if (m->m_flags & M_PKTHDR)
+			(*pr)(", pktlen %d", m->m_pkthdr.len);
+		(*pr)(", len %zu, size %zu\n", len, size);
+	}
+	indent = "\\--";
+	if (v != NULL)
+		(*pr)("%s total packets %zu\n", indent, pkts);
+}
 #endif
 
 /*
-- 
2.20.1