From: Jeff Lucovsky <jlucovsky@oisf.net>
Date: Mon, 16 Jun 2025 14:04:48 +0000 (-0400)
Subject: util/mtu: Avoid excessive ioctls for MTU
X-Git-Tag: suricata-8.0.0~63
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=e8753b9ba78cf54b1b8db65b646f09d71bc10f8d;p=thirdparty%2Fsuricata.git

util/mtu: Avoid excessive ioctls for MTU

Issue: 7643

Use the cached livedev MTU value, when available.
---

diff --git a/src/util-ioctl.c b/src/util-ioctl.c
index 813a5590cd..d335ecce19 100644
--- a/src/util-ioctl.c
+++ b/src/util-ioctl.c
@@ -127,13 +127,16 @@ int GetIfaceMaxPacketSize(LiveDevice *ld)
     if ((dev == NULL) || strlen(dev) == 0)
         return 0;
 
-    int mtu = GetIfaceMTU(dev);
-    switch (mtu) {
-        case 0:
-        case -1:
-            return 0;
+    int mtu = ld->mtu;
+    if (ld->mtu == 0) {
+        mtu = GetIfaceMTU(dev);
+        switch (mtu) {
+            case 0:
+            case -1:
+                return 0;
+        }
+        ld->mtu = mtu;
     }
-    ld->mtu = mtu;
     int ll_header = GetIfaceMaxHWHeaderLength(dev);
     return ll_header + mtu;
 }