From: Michael Tremer <michael.tremer@ipfire.org>
Date: Fri, 10 Feb 2023 10:13:37 +0000 (+0000)
Subject: networkd: Read link MTU
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f37df5ea0920add075e294db28a3ec5ed83b0fe5;p=network.git

networkd: Read link MTU

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/networkd/link.c b/src/networkd/link.c
index 40f809f5..62be8937 100644
--- a/src/networkd/link.c
+++ b/src/networkd/link.c
@@ -40,6 +40,11 @@ struct nw_link {
 
 	// Interface Name
 	char ifname[IF_NAMESIZE];
+
+	// MTU
+	uint32_t mtu;
+	uint32_t min_mtu;
+	uint32_t max_mtu;
 };
 
 int nw_link_create(struct nw_link** link, struct nw_daemon* daemon, int ifindex) {
@@ -115,6 +120,54 @@ static int nw_link_update_ifname(struct nw_link* link, sd_netlink_message* messa
 	return 0;
 }
 
+static int nw_link_update_mtu(struct nw_link* link, sd_netlink_message* message) {
+	uint32_t mtu = 0;
+	uint32_t min_mtu = 0;
+	uint32_t max_mtu = 0;
+	int r;
+
+	// Read the MTU
+	r = sd_netlink_message_read_u32(message, IFLA_MTU, &mtu);
+	if (r < 0) {
+		ERROR("Could not read MTU for link %d: %m\n", link->ifindex);
+		return r;
+	}
+
+	// Read the minimum MTU
+	r = sd_netlink_message_read_u32(message, IFLA_MIN_MTU, &min_mtu);
+	if (r < 0) {
+		ERROR("Could not read the minimum MTU for link %d: %m\n", link->ifindex);
+		return r;
+	}
+
+	// Read the maximum MTU
+	r = sd_netlink_message_read_u32(message, IFLA_MAX_MTU, &max_mtu);
+	if (r < 0) {
+		ERROR("Could not read the maximum MTU for link %d: %m\n", link->ifindex);
+		return r;
+	}
+
+	// Set the maximum MTU to infinity
+	if (!max_mtu)
+		max_mtu = UINT32_MAX;
+
+	// Store min/max MTU
+	link->min_mtu = min_mtu;
+	link->max_mtu = max_mtu;
+
+	// End here, if the MTU has not been changed
+	if (link->mtu == mtu)
+		return 0;
+
+	DEBUG("Link %d: MTU has changed to %" PRIu32 " (min: %" PRIu32 ", max: %" PRIu32 ")\n",
+		link->ifindex, link->mtu, link->min_mtu, link->max_mtu);
+
+	// Store MTU
+	link->mtu = mtu;
+
+	return 0;
+}
+
 /*
 	This function is called whenever anything changes, so that we can
 	update our internal link object.
@@ -127,6 +180,11 @@ static int nw_link_update(struct nw_link* link, sd_netlink_message* message) {
 	if (r)
 		return r;
 
+	// Update the MTU
+	r = nw_link_update_mtu(link, message);
+	if (r)
+		return r;
+
 	return 0;
 }