Only in rp-pppoe-3.10+sa: .auto-nanorc
diff -r -U4 rp-pppoe-3.10/src/pppoe.h rp-pppoe-3.10+sa/src/pppoe.h
--- rp-pppoe-3.10/src/pppoe.h	2008-06-30 15:00:43.000000000 +0100
+++ rp-pppoe-3.10+sa/src/pppoe.h	2010-05-02 12:33:57.000000000 +0100
@@ -179,8 +179,9 @@
 #define TAG_HOST_UNIQ          0x0103
 #define TAG_AC_COOKIE          0x0104
 #define TAG_VENDOR_SPECIFIC    0x0105
 #define TAG_RELAY_SESSION_ID   0x0110
+#define TAG_PPP_MAX_PAYLOAD    0x0120
 #define TAG_SERVICE_NAME_ERROR 0x0201
 #define TAG_AC_SYSTEM_ERROR    0x0202
 #define TAG_GENERIC_ERROR      0x0203
 
diff -r -U4 rp-pppoe-3.10/src/pppoe-server.c rp-pppoe-3.10+sa/src/pppoe-server.c
--- rp-pppoe-3.10/src/pppoe-server.c	2008-06-30 15:00:43.000000000 +0100
+++ rp-pppoe-3.10+sa/src/pppoe-server.c	2010-05-02 12:53:38.000000000 +0100
@@ -57,8 +57,10 @@
 #include <time.h>
 
 #include <signal.h>
 
+#include <sys/ioctl.h>
+
 #ifdef HAVE_LICENSE
 #include "license.h"
 #include "licensed-only/servfuncs.h"
 static struct License const *ServerLicense;
@@ -685,8 +687,21 @@
 	    plen += TAG_HDR_SIZE+slen;
 	}
     }
 
+    /* Add our maximum MRU */
+    {
+	PPPoETag maxPayload;
+	UINT16_t mru = htons(ethif->mru);
+	maxPayload.type = htons(TAG_PPP_MAX_PAYLOAD);
+	maxPayload.length = htons(sizeof(mru));
+	memcpy(maxPayload.payload, &mru, sizeof(mru));
+	CHECK_ROOM(cursor, pado.payload, sizeof(mru) + TAG_HDR_SIZE);
+	memcpy(cursor, &maxPayload, sizeof(mru) + TAG_HDR_SIZE);
+	cursor += sizeof(mru) + TAG_HDR_SIZE;
+	plen += sizeof(mru) + TAG_HDR_SIZE;
+    }
+
     CHECK_ROOM(cursor, pado.payload, TAG_HDR_SIZE + COOKIE_LEN);
     memcpy(cursor, &cookie, TAG_HDR_SIZE + COOKIE_LEN);
     cursor += TAG_HDR_SIZE + COOKIE_LEN;
     plen += TAG_HDR_SIZE + COOKIE_LEN;
@@ -988,8 +1003,20 @@
 	memcpy(cursor, &hostUniq, ntohs(hostUniq.length) + TAG_HDR_SIZE);
 	cursor += ntohs(hostUniq.length) + TAG_HDR_SIZE;
 	plen += ntohs(hostUniq.length) + TAG_HDR_SIZE;
     }
+    /* Add our maximum MRU */
+    {
+	PPPoETag maxPayload;
+	UINT16_t mru = htons(ethif->mru);
+	maxPayload.type = htons(TAG_PPP_MAX_PAYLOAD);
+	maxPayload.length = htons(sizeof(mru));
+	memcpy(maxPayload.payload, &mru, sizeof(mru));
+	CHECK_ROOM(cursor, pads.payload, sizeof(mru) + TAG_HDR_SIZE);
+	memcpy(cursor, &maxPayload, sizeof(mru) + TAG_HDR_SIZE);
+	cursor += sizeof(mru) + TAG_HDR_SIZE;
+	plen += sizeof(mru) + TAG_HDR_SIZE;
+    }
     pads.length = htons(plen);
     sendPacket(NULL, sock, &pads, (int) (plen + HDR_SIZE));
 
     /* Close sock; don't need it any more */
@@ -1460,9 +1487,32 @@
     }
 
     /* Open all the interfaces */
     for (i=0; i<NumInterfaces; i++) {
+	int s;
+	struct ifreq ifr;
+
 	interfaces[i].sock = openInterface(interfaces[i].name, Eth_PPPOE_Discovery, interfaces[i].mac);
+
+	/* Update maximum MRU */
+	s = socket(PF_INET, SOCK_DGRAM, 0);
+	if (s < 0)
+	    s = socket(PF_PACKET, SOCK_DGRAM, 0);
+	if (s < 0)
+	    s = socket(PF_INET6, SOCK_DGRAM, 0);
+	if (s < 0)
+	    s = socket(PF_UNIX, SOCK_DGRAM, 0);
+	if (s < 0) {
+	    interfaces[i].mru = 1492;
+	} else {
+	    strncpy(ifr.ifr_name, interfaces[i].name, sizeof(ifr.ifr_name));
+	    if (ioctl(s, SIOCGIFMTU, &ifr) < 0) {
+		interfaces[i].mru = 1492;
+	    } else {
+		interfaces[i].mru = ifr.ifr_mtu - 8;
+	    }
+	    close(s);
+	}
     }
 
     /* Ignore SIGPIPE */
     signal(SIGPIPE, SIG_IGN);
diff -r -U4 rp-pppoe-3.10/src/pppoe-server.h rp-pppoe-3.10+sa/src/pppoe-server.h
--- rp-pppoe-3.10/src/pppoe-server.h	2008-06-30 15:00:43.000000000 +0100
+++ rp-pppoe-3.10+sa/src/pppoe-server.h	2010-05-02 12:38:26.000000000 +0100
@@ -28,8 +28,9 @@
     char name[IFNAMSIZ+1];	/* Interface name */
     int sock;			/* Socket for discovery frames */
     unsigned char mac[ETH_ALEN]; /* MAC address */
     EventHandler *eh;		/* Event handler for this interface */
+    int mru;
 
     /* Next fields are used only if we're an L2TP LAC */
 #ifdef HAVE_L2TP
     int session_sock;		/* Session socket */