X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/55bc97e626e0f31e04b190528b25c6e026942610..211cd6277e10a6402a4f7abb41dc8b0829b04ada:/netlink.c

diff --git a/netlink.c b/netlink.c
index 6384c02..0dd4450 100644
--- a/netlink.c
+++ b/netlink.c
@@ -120,7 +120,7 @@ their use.
 #define ICMP_CODE_TTL_EXCEEDED           0
 
 /* Generic IP checksum routine */
-static inline uint16_t ip_csum(uint8_t *iph,int32_t count)
+static inline uint16_t ip_csum(const uint8_t *iph,int32_t count)
 {
     register uint32_t sum=0;
 
@@ -144,7 +144,7 @@ static inline uint16_t ip_csum(uint8_t *iph,int32_t count)
  *      By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
  *      Arnt Gulbrandsen.
  */
-static inline uint16_t ip_fast_csum(uint8_t *iph, int32_t ihl) {
+static inline uint16_t ip_fast_csum(const uint8_t *iph, int32_t ihl) {
     uint32_t sum;
 
     __asm__ __volatile__(
@@ -193,6 +193,10 @@ struct iphdr {
     uint16_t   tot_len;
     uint16_t   id;
     uint16_t   frag_off;
+#define IPHDR_FRAG_OFF  ((uint16_t)0x1fff)
+#define IPHDR_FRAG_MORE ((uint16_t)0x2000)
+#define IPHDR_FRAG_DONT ((uint16_t)0x4000)
+/*                 reserved        0x8000 */
     uint8_t    ttl;
     uint8_t    protocol;
     uint16_t   check;
@@ -206,7 +210,7 @@ struct icmphdr {
     uint8_t type;
     uint8_t code;
     uint16_t check;
-    union {
+    union icmpinfofield {
 	uint32_t unused;
 	struct {
 	    uint8_t pointer;
@@ -220,6 +224,8 @@ struct icmphdr {
 	} echo;
     } d;
 };
+
+static const union icmpinfofield icmp_noinfo;
     
 static void netlink_packet_deliver(struct netlink *st,
 				   struct netlink_client *client,
@@ -298,14 +304,22 @@ static bool_t netlink_icmp_may_reply(struct buffer_if *buf)
     icmph=(struct icmphdr *)buf->start;
     if (iph->protocol==1) {
 	switch(icmph->type) {
-	case 3: /* Destination unreachable */
-	case 11: /* Time Exceeded */
-	case 12: /* Parameter Problem */
+	    /* Based on http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml#icmp-parameters-types
+	     * as retrieved Thu, 20 Mar 2014 00:16:44 +0000.
+	     * Deprecated, reserved, unassigned and experimental
+	     * options are treated as not safe to reply to.
+	     */
+	case 0: /* Echo Reply */
+	case 8: /* Echo */
+	case 13: /* Timestamp */
+	case 14: /* Timestamp Reply */
+	    return True;
+	default:
 	    return False;
 	}
     }
     /* How do we spot broadcast destination addresses? */
-    if (ntohs(iph->frag_off)&0x1fff) return False; /* Non-initial fragment */
+    if (ntohs(iph->frag_off)&IPHDR_FRAG_OFF) return False;
     source=ntohl(iph->saddr);
     if (source==0) return False;
     if ((source&0xff000000)==0x7f000000) return False;
@@ -354,7 +368,8 @@ static uint16_t netlink_icmp_reply_len(struct buffer_if *buf)
    comes from. NULL indicates the host. */
 static void netlink_icmp_simple(struct netlink *st, struct buffer_if *buf,
 				struct netlink_client *client,
-				uint8_t type, uint8_t code)
+				uint8_t type, uint8_t code,
+				union icmpinfofield info)
 {
     struct icmphdr *h;
     uint16_t len;
@@ -363,7 +378,7 @@ static void netlink_icmp_simple(struct netlink *st, struct buffer_if *buf,
 	struct iphdr *iph=(struct iphdr *)buf->start;
 	len=netlink_icmp_reply_len(buf);
 	h=netlink_icmp_tmpl(st,ntohl(iph->saddr),len);
-	h->type=type; h->code=code;
+	h->type=type; h->code=code; h->d=info;
 	memcpy(buf_append(&st->icmp,len),buf->start,len);
 	netlink_icmp_csum(h);
 	netlink_packet_deliver(st,NULL,&st->icmp);
@@ -521,7 +536,7 @@ static void netlink_packet_deliver(struct netlink *st,
 		    "(s=%s, d=%s)\n", st->name, s, d);
 	    free(s); free(d);
 	    netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-				ICMP_CODE_NET_UNREACHABLE);
+				ICMP_CODE_NET_UNREACHABLE, icmp_noinfo);
 	    BUF_FREE(buf);
 	}
     } else {
@@ -538,7 +553,7 @@ static void netlink_packet_deliver(struct netlink *st,
 	    free(s); free(d);
 		    
 	    netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-				ICMP_CODE_NET_PROHIBITED);
+				ICMP_CODE_NET_PROHIBITED, icmp_noinfo);
 	    BUF_FREE(buf);
 	} else {
 	    if (best_quality>0) {
@@ -548,8 +563,10 @@ static void netlink_packet_deliver(struct netlink *st,
 		BUF_ASSERT_FREE(buf);
 	    } else {
 		/* Generate ICMP destination unreachable */
-		netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-				    ICMP_CODE_NET_UNREACHABLE); /* client==NULL */
+		netlink_icmp_simple(st,buf,client,/* client==NULL */
+				    ICMP_TYPE_UNREACHABLE,
+				    ICMP_CODE_NET_UNREACHABLE,
+				    icmp_noinfo);
 		BUF_FREE(buf);
 	    }
 	}
@@ -570,7 +587,7 @@ static void netlink_packet_forward(struct netlink *st,
     if (iph->ttl<=1) {
 	/* Generate ICMP time exceeded */
 	netlink_icmp_simple(st,buf,client,ICMP_TYPE_TIME_EXCEEDED,
-			    ICMP_CODE_TTL_EXCEEDED);
+			    ICMP_CODE_TTL_EXCEEDED,icmp_noinfo);
 	BUF_FREE(buf);
 	return;
     }
@@ -599,7 +616,7 @@ static void netlink_packet_local(struct netlink *st,
     }
     h=(struct icmphdr *)buf->start;
 
-    if ((ntohs(h->iph.frag_off)&0xbfff)!=0) {
+    if ((ntohs(h->iph.frag_off)&(IPHDR_FRAG_OFF|IPHDR_FRAG_MORE))!=0) {
 	Message(M_WARNING,"%s: fragmented packet addressed to secnet; "
 		"ignoring it\n",st->name);
 	BUF_FREE(buf);
@@ -625,7 +642,7 @@ static void netlink_packet_local(struct netlink *st,
     } else {
 	/* Send ICMP protocol unreachable */
 	netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-			    ICMP_CODE_PROTOCOL_UNREACHABLE);
+			    ICMP_CODE_PROTOCOL_UNREACHABLE,icmp_noinfo);
 	BUF_FREE(buf);
 	return;
     }
@@ -765,7 +782,7 @@ static void netlink_dump_routes(struct netlink *st, bool_t requested)
     if (requested) c=M_WARNING;
     if (st->ptp) {
 	net=ipaddr_to_string(st->secnet_address);
-	Message(c,"%s: point-to-point (remote end is %s); routes:\n",
+	Message(c,"%s: point-to-point (remote end is %s); routes: ",
 		st->name, net);
 	free(net);
 	netlink_output_subnets(st,c,st->clients->subnets);