[PATCH iproute2-next v5] ip/bond: add lacp_strict support

[Louis Scalbert <louis.scalbert@6wind.com>]

lacp_strict defines the behavior of a LACP bonding interface
when no slaves are in Collecting_Distributing state while at least
'min_links' slaves have carrier.

In the default (off) mode, the bonding master remains up and a
single slave is selected for TX/RX, while traffic received on other
slaves is dropped. This preserves the existing behavior.

In lacp_strict mode, the bonding master reports carrier down in this
situation.

Link: https://lore.kernel.org/netdev/20260603150331.1919611-1-louis.scalbert@6wind.com/
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>
---
 include/uapi/linux/if_link.h |  1 +
 ip/iplink_bond.c             | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 70aee114..d3a21fba 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -1601,6 +1601,7 @@ enum {
 	IFLA_BOND_NS_IP6_TARGET,
 	IFLA_BOND_COUPLED_CONTROL,
 	IFLA_BOND_BROADCAST_NEIGH,
+	IFLA_BOND_LACP_STRICT,
 	__IFLA_BOND_MAX,
 };
 
diff --git a/ip/iplink_bond.c b/ip/iplink_bond.c
index 714fe7bd..7e2e397a 100644
--- a/ip/iplink_bond.c
+++ b/ip/iplink_bond.c
@@ -87,6 +87,12 @@ static const char *lacp_rate_tbl[] = {
 	NULL,
 };
 
+static const char *lacp_strict_tbl[] = {
+	"off",
+	"on",
+	NULL,
+};
+
 static const char *ad_select_tbl[] = {
 	"stable",
 	"bandwidth",
@@ -155,6 +161,7 @@ static void print_explain(FILE *f)
 		"                [ ad_user_port_key PORTKEY ]\n"
 		"                [ ad_actor_sys_prio SYSPRIO ]\n"
 		"                [ ad_actor_system LLADDR ]\n"
+		"                [ lacp_strict LACP_STRICT ]\n"
 		"                [ arp_missed_max MISSED_MAX ]\n"
 		"\n"
 		"BONDMODE := balance-rr|active-backup|balance-xor|broadcast|802.3ad|balance-tlb|balance-alb\n"
@@ -168,6 +175,7 @@ static void print_explain(FILE *f)
 		"AD_SELECT := stable|bandwidth|count\n"
 		"COUPLED_CONTROL := off|on\n"
 		"BROADCAST_NEIGHBOR := off|on\n"
+		"LACP_STRICT := off|on\n"
 	);
 }
 
@@ -188,6 +196,7 @@ static int bond_parse_opt(struct link_util *lu, int argc, char **argv,
 	__u32 packets_per_slave;
 	__u8 missed_max;
 	__u8 broadcast_neighbor;
+	__u8 lacp_strict;
 	unsigned int ifindex;
 	int ret;
 
@@ -417,6 +426,13 @@ static int bond_parse_opt(struct link_util *lu, int argc, char **argv,
 				return -1;
 			addattr_l(n, 1024, IFLA_BOND_AD_ACTOR_SYSTEM,
 				  abuf, len);
+		} else if (matches(*argv, "lacp_strict") == 0) {
+			NEXT_ARG();
+			lacp_strict = parse_on_off("lacp_strict", *argv, &ret);
+			if (ret)
+				return ret;
+			lacp_strict = get_index(lacp_strict_tbl, *argv);
+			addattr8(n, 1024, IFLA_BOND_LACP_STRICT, lacp_strict);
 		} else if (matches(*argv, "tlb_dynamic_lb") == 0) {
 			NEXT_ARG();
 			if (get_u8(&tlb_dynamic_lb, *argv, 0)) {
@@ -642,6 +658,10 @@ static void bond_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 			   "all_slaves_active %u ",
 			   rta_getattr_u8(tb[IFLA_BOND_ALL_SLAVES_ACTIVE]));
 
+	if (tb[IFLA_BOND_LACP_STRICT])
+		print_on_off(PRINT_ANY, "lacp_strict", "lacp_strict %s ",
+			     rta_getattr_u8(tb[IFLA_BOND_LACP_STRICT]));
+
 	if (tb[IFLA_BOND_MIN_LINKS])
 		print_uint(PRINT_ANY,
 			   "min_links",
-- 
2.39.2