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-rw-r--r--usr.sbin/natd/icmp.c112
1 files changed, 112 insertions, 0 deletions
diff --git a/usr.sbin/natd/icmp.c b/usr.sbin/natd/icmp.c
new file mode 100644
index 0000000..40464ff
--- /dev/null
+++ b/usr.sbin/natd/icmp.c
@@ -0,0 +1,112 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <ctype.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <errno.h>
+#include <signal.h>
+
+#include <netdb.h>
+
+#include <netinet/in.h>
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+#include <machine/in_cksum.h>
+
+#include <alias.h>
+
+#include "natd.h"
+
+int SendNeedFragIcmp (int sock, struct ip* failedDgram, int mtu)
+{
+ char icmpBuf[IP_MAXPACKET];
+ struct ip* ip;
+ struct icmp* icmp;
+ int icmpLen;
+ int failBytes;
+ int failHdrLen;
+ struct sockaddr_in addr;
+ int wrote;
+ struct in_addr swap;
+/*
+ * Don't send error if packet is
+ * not the first fragment.
+ */
+ if (ntohs (failedDgram->ip_off) & ~(IP_MF | IP_DF))
+ return 0;
+/*
+ * Dont respond if failed datagram is ICMP.
+ */
+ if (failedDgram->ip_p == IPPROTO_ICMP)
+ return 0;
+/*
+ * Start building the message.
+ */
+ ip = (struct ip*) icmpBuf;
+ icmp = (struct icmp*) (icmpBuf + sizeof (struct ip));
+/*
+ * Complete ICMP part.
+ */
+ icmp->icmp_type = ICMP_UNREACH;
+ icmp->icmp_code = ICMP_UNREACH_NEEDFRAG;
+ icmp->icmp_cksum = 0;
+ icmp->icmp_void = 0;
+ icmp->icmp_nextmtu = htons (mtu);
+/*
+ * Copy header + 64 bits of original datagram.
+ */
+ failHdrLen = (failedDgram->ip_hl << 2);
+ failBytes = failedDgram->ip_len - failHdrLen;
+ if (failBytes > 8)
+ failBytes = 8;
+
+ failBytes += failHdrLen;
+ icmpLen = ICMP_MINLEN + failBytes;
+
+ memcpy (&icmp->icmp_ip, failedDgram, failBytes);
+/*
+ * Calculate checksum.
+ */
+ icmp->icmp_cksum = InternetChecksum ((u_short*) icmp, icmpLen);
+/*
+ * Add IP header using old IP header as template.
+ */
+ memcpy (ip, failedDgram, sizeof (struct ip));
+
+ ip->ip_v = 4;
+ ip->ip_hl = 5;
+ ip->ip_len = htons (sizeof (struct ip) + icmpLen);
+ ip->ip_p = IPPROTO_ICMP;
+ ip->ip_tos = 0;
+
+ swap = ip->ip_dst;
+ ip->ip_dst = ip->ip_src;
+ ip->ip_src = swap;
+
+ PacketAliasIn ((char*) ip, IP_MAXPACKET);
+
+ addr.sin_family = AF_INET;
+ addr.sin_addr = ip->ip_dst;
+ addr.sin_port = 0;
+/*
+ * Put packet into processing queue.
+ */
+ wrote = sendto (sock,
+ icmp,
+ icmpLen,
+ 0,
+ (struct sockaddr*) &addr,
+ sizeof addr);
+
+ if (wrote != icmpLen)
+ Warn ("Cannot send ICMP message.");
+
+ return 1;
+}
+
+
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