git: 4c932a4d45fb - main - netlink: decode netlink message flags symbolically

The branch main has been updated by kp:

URL: https://cgit.FreeBSD.org/src/commit/?id=4c932a4d45fb3130ffa80176f5ff9dcacabd49f1

commit 4c932a4d45fb3130ffa80176f5ff9dcacabd49f1
Author:     Ishan Agrawal <iagrawal9990@gmail.com>
AuthorDate: 2026-06-24 04:08:07 +0000
Commit:     Kristof Provost <kp@FreeBSD.org>
CommitDate: 2026-06-24 12:15:20 +0000

    netlink: decode netlink message flags symbolically
    
    Generate an nlm_flag table definition for mktable from
    netlink/netlink.h, add a sysdecode_nlm_flag() helper to
    libsysdecode, and use it when decoding netlink message headers.
    
    This enables mktable to generate netlink message flag lookup tables and
    replaces raw hexadecimal output for recognized NLM_F_* flag values
    with their symbolic names.
    
    Reviewed by:    kp
    Signed-off-by:  Ishan Agrawal <iagrawal9990@gmail.com>
    Sponsored by:   Google LLC (GSoC 2026)
    Pull Request:   https://github.com/freebsd/freebsd-src/pull/2294
---
 lib/libsysdecode/flags.c     | 8 ++++++++
 lib/libsysdecode/mktables    | 1 +
 lib/libsysdecode/netlink.c   | 7 +++++--
 lib/libsysdecode/sysdecode.h | 3 ++-
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/lib/libsysdecode/flags.c b/lib/libsysdecode/flags.c
index 8009a7a2f97e..983314e56369 100644
--- a/lib/libsysdecode/flags.c
+++ b/lib/libsysdecode/flags.c
@@ -70,6 +70,7 @@
 #include <netgraph/bluetooth/include/ng_l2cap.h>
 #include <netgraph/bluetooth/include/ng_btsocket.h>
 #include <netpfil/pf/pf_nl.h>
+#include <netlink/netlink.h>
 
 #include "support.h"
 
@@ -1215,3 +1216,10 @@ sysdecode_pfnl_cmd(int cmd)
 
 	return (lookup_value(pfnl_cmd, cmd));
 }
+
+const char *
+sysdecode_nlm_flag(int flag)
+{
+
+	return (lookup_value(nlm_flag, flag));
+}
diff --git a/lib/libsysdecode/mktables b/lib/libsysdecode/mktables
index 2bfbaf529f44..df794b74c168 100644
--- a/lib/libsysdecode/mktables
+++ b/lib/libsysdecode/mktables
@@ -171,6 +171,7 @@ fi
 gen_table "shmflags"  "SHM_[A-Z_]+[[:space:]]+0x[0-9]+"                    "sys/mman.h"         "SHM_ANON"
 gen_table "itimerwhich"     "ITIMER_[A-Z]+[[:space:]]+[0-9]+"              "sys/time.h"
 gen_table "pfnl_cmd"        "PFNL_CMD_[A-Z_]+[[:space:]]+[0-9]+"           "netpfil/pf/pf_nl.h"
+gen_table "nlm_flag"        "NLM_F_[A-Z]+[[:space:]]+0x[0-9]+"             "netlink/netlink.h"
 
 # Generate a .depend file for our output file
 if [ -n "$output_file" ]; then
diff --git a/lib/libsysdecode/netlink.c b/lib/libsysdecode/netlink.c
index a28a0a061134..2143a0d391a5 100644
--- a/lib/libsysdecode/netlink.c
+++ b/lib/libsysdecode/netlink.c
@@ -73,8 +73,11 @@ sysdecode_netlink(FILE *fp, const void *buf, size_t len)
 		}
 
 		fprintf(fp, ",flags=");
-		/* TODO: decode flags symbolically using sysdecode_mask. */
-		fprintf(fp, "0x%x", nl->nlmsg_flags);
+		const char *nlm_f = sysdecode_nlm_flag(nl->nlmsg_flags);
+		if (nlm_f != NULL)
+			fprintf(fp, "%s", nlm_f);
+		else
+			fprintf(fp, "0x%x", nl->nlmsg_flags);
 
 		fprintf(fp, ",seq=%u,pid=%u", nl->nlmsg_seq, nl->nlmsg_pid);
 
diff --git a/lib/libsysdecode/sysdecode.h b/lib/libsysdecode/sysdecode.h
index 4675b1e3c463..3675a582a9b8 100644
--- a/lib/libsysdecode/sysdecode.h
+++ b/lib/libsysdecode/sysdecode.h
@@ -66,7 +66,8 @@ const char *sysdecode_ipproto(int _protocol);
 void	sysdecode_kevent_fflags(FILE *_fp, short _filter, int _fflags,
 	    int _base);
 const char *sysdecode_itimer(int _which);
-const char *sysdecode_pfnl_cmd(int cmd);
+const char *sysdecode_pfnl_cmd(int _cmd);
+const char *sysdecode_nlm_flag(int _flag);
 const char *sysdecode_kevent_filter(int _filter);
 bool	sysdecode_kevent_flags(FILE *_fp, int _flags, int *_rem);
 const char *sysdecode_kldsym_cmd(int _cmd);