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-rw-r--r--mtu.c364
1 files changed, 364 insertions, 0 deletions
diff --git a/mtu.c b/mtu.c
new file mode 100644
index 0000000..b1f7ae7
--- /dev/null
+++ b/mtu.c
@@ -0,0 +1,364 @@
+#include <errno.h>
+#include <netdb.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <asm/types.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
+
+struct sockaddr_in whereto;
+u_char inpack[0x10000];
+u_char outpack[0x10000];
+int mtu_size;
+
+static char *pr_addr(__u32 addr)
+{
+ struct hostent *hp;
+ static char buf[4096];
+
+ sprintf(buf, "%s", inet_ntoa(*(struct in_addr *)&addr));
+ return buf;
+}
+
+static void pr_icmph(__u8 type, __u8 code, __u32 info, struct icmphdr *icp)
+{
+ switch(type) {
+ case ICMP_ECHOREPLY:
+ printf("Echo Reply\n");
+ /* XXX ID + Seq + Data */
+ break;
+ case ICMP_DEST_UNREACH:
+ switch(code) {
+ case ICMP_NET_UNREACH:
+ printf("Destination Net Unreachable\n");
+ break;
+ case ICMP_HOST_UNREACH:
+ printf("Destination Host Unreachable\n");
+ break;
+ case ICMP_PROT_UNREACH:
+ printf("Destination Protocol Unreachable\n");
+ break;
+ case ICMP_PORT_UNREACH:
+ printf("Destination Port Unreachable\n");
+ break;
+ case ICMP_FRAG_NEEDED:
+ printf("Frag needed and DF set (mtu = %u)\n", info);
+ break;
+ case ICMP_SR_FAILED:
+ printf("Source Route Failed\n");
+ break;
+ case ICMP_PKT_FILTERED:
+ printf("Packet filtered\n");
+ break;
+ default:
+ printf("Dest Unreachable, Bad Code: %d\n", code);
+ break;
+ }
+ break;
+ case ICMP_SOURCE_QUENCH:
+ printf("Source Quench\n");
+ break;
+ case ICMP_REDIRECT:
+ switch(code) {
+ case ICMP_REDIR_NET:
+ printf("Redirect Network");
+ break;
+ case ICMP_REDIR_HOST:
+ printf("Redirect Host");
+ break;
+ case ICMP_REDIR_NETTOS:
+ printf("Redirect Type of Service and Network");
+ break;
+ case ICMP_REDIR_HOSTTOS:
+ printf("Redirect Type of Service and Host");
+ break;
+ default:
+ printf("Redirect, Bad Code: %d", code);
+ break;
+ }
+ if (icp)
+ printf("(New nexthop: %s)\n", pr_addr(icp->un.gateway));
+ break;
+ case ICMP_ECHO:
+ printf("Echo Request\n");
+ /* XXX ID + Seq + Data */
+ break;
+ case ICMP_TIME_EXCEEDED:
+ switch(code) {
+ case ICMP_EXC_TTL:
+ printf("Time to live exceeded\n");
+ break;
+ case ICMP_EXC_FRAGTIME:
+ printf("Frag reassembly time exceeded\n");
+ break;
+ default:
+ printf("Time exceeded, Bad Code: %d\n", code);
+ break;
+ }
+ break;
+ case ICMP_PARAMETERPROB:
+ printf("Parameter problem: pointer = %u\n", icp ? (ntohl(icp->un.gateway)>>24) : info);
+ break;
+ case ICMP_TIMESTAMP:
+ printf("Timestamp\n");
+ /* XXX ID + Seq + 3 timestamps */
+ break;
+ case ICMP_TIMESTAMPREPLY:
+ printf("Timestamp Reply\n");
+ /* XXX ID + Seq + 3 timestamps */
+ break;
+ case ICMP_INFO_REQUEST:
+ printf("Information Request\n");
+ /* XXX ID + Seq */
+ break;
+ case ICMP_INFO_REPLY:
+ printf("Information Reply\n");
+ /* XXX ID + Seq */
+ break;
+#ifdef ICMP_MASKREQ
+ case ICMP_MASKREQ:
+ printf("Address Mask Request\n");
+ break;
+#endif
+#ifdef ICMP_MASKREPLY
+ case ICMP_MASKREPLY:
+ printf("Address Mask Reply\n");
+ break;
+#endif
+ default:
+ printf("Bad ICMP type: %d\n", type);
+ }
+}
+
+static u_short in_cksum(const u_short *addr, register int len, u_short csum)
+{
+ register int nleft = len;
+ const u_short *w = addr;
+ register u_short answer;
+ register int sum = csum;
+
+ while (nleft > 1) {
+ sum += *w++;
+ nleft -= 2;
+ }
+
+ if (nleft == 1)
+ sum += htons(*(u_char *)w << 8);
+
+ sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
+ sum += (sum >> 16); /* add carry */
+ answer = ~sum; /* truncate to 16 bits */
+ return (answer);
+}
+
+int send_probe(int icmp_sock, int *seq)
+{
+ struct icmphdr *icp;
+ int i, cc = mtu_size - sizeof(struct iphdr);
+
+ icp = (struct icmphdr *)outpack;
+ icp->type = ICMP_ECHO;
+ icp->code = 0;
+ icp->checksum = 0;
+ icp->un.echo.sequence = htons(++(*seq));
+ icp->un.echo.id = getpid();
+ icp->checksum = in_cksum((u_short *)icp, cc, 0);
+
+ printf("To %s: icmp_seq=%u bytes=%d\n",
+ pr_addr(whereto.sin_addr.s_addr),
+ ntohs(icp->un.echo.sequence), cc);
+
+ i = sendto(icmp_sock, outpack, cc, 0,
+ (struct sockaddr *) &whereto, sizeof(whereto));
+
+ return (cc == i ? 0 : i);
+}
+
+int send_frag_needed(int icmp_sock, struct iphdr *iph, int newmtu)
+{
+ struct icmphdr *icp;
+ int i, cc = sizeof(struct icmphdr) + sizeof(struct iphdr) + 8;
+
+ icp = (struct icmphdr *) outpack;
+ icp->type = ICMP_DEST_UNREACH;
+ icp->code = ICMP_FRAG_NEEDED;
+ icp->checksum = 0;
+ icp->un.frag.__unused = 0;
+ icp->un.frag.mtu = htons(newmtu);
+
+ /* copy ip header + 64-bits of original packet */
+ memcpy(icp + 1, iph, sizeof(struct iphdr) + 8);
+
+ icp->checksum = in_cksum((u_short *)icp, cc, 0);
+
+ printf("To %s: frag_needed mtu=%d\n",
+ pr_addr(whereto.sin_addr.s_addr),
+ mtu_size - 2);
+
+ i = sendto(icmp_sock, outpack, cc, 0,
+ (struct sockaddr *) &whereto, sizeof(whereto));
+
+ return (cc == i ? 0 : i);
+}
+
+/*
+ * parse_reply --
+ * Print out the packet, if it came from us. This logic is necessary
+ * because ALL readers of the ICMP socket get a copy of ALL ICMP packets
+ * which arrive ('tis only fair). This permits multiple copies of this
+ * program to be run without having intermingled output (or statistics!).
+ */
+int
+parse_reply(int icmp_sock, __u8 *buf, int cc, void *addr)
+{
+ struct sockaddr_in *from = addr;
+ struct icmphdr *icp;
+ struct iphdr *ip;
+ int hlen;
+ int csfailed;
+
+ /* Check the IP header */
+ ip = (struct iphdr *)buf;
+ hlen = ip->ihl*4;
+ if (cc < hlen + 8 || ip->ihl < 5) {
+ return 1;
+ }
+
+ /* Now the ICMP part */
+ cc -= hlen;
+ icp = (struct icmphdr *)(buf + hlen);
+ csfailed = in_cksum((u_short *)icp, cc, 0);
+
+ if (icp->type == ICMP_ECHOREPLY) {
+ if (icp->un.echo.id != getpid())
+ return 1; /* 'Twas not our ECHO */
+
+ printf("From %s: icmp_seq=%u bytes=%d\n",
+ pr_addr(from->sin_addr.s_addr),
+ ntohs(icp->un.echo.sequence),
+ cc);
+
+ if (cc+hlen >= mtu_size - 2)
+ send_frag_needed(icmp_sock, ip, mtu_size - 2);
+ } else {
+ /* We fall here when a redirect or source quench arrived.
+ * Also this branch processes icmp errors, when IP_RECVERR
+ * is broken. */
+
+ switch (icp->type) {
+ case ICMP_ECHO:
+ /* MUST NOT */
+ return 1;
+ case ICMP_SOURCE_QUENCH:
+ case ICMP_REDIRECT:
+ case ICMP_DEST_UNREACH:
+ case ICMP_TIME_EXCEEDED:
+ case ICMP_PARAMETERPROB:
+ {
+ struct iphdr * iph = (struct iphdr *)(&icp[1]);
+ struct icmphdr *icp1 = (struct icmphdr*)((unsigned char *)iph + iph->ihl*4);
+ int error_pkt;
+ if (cc < 8+sizeof(struct iphdr)+8 ||
+ cc < 8+iph->ihl*4+8)
+ return 1;
+ if (icp1->type != ICMP_ECHO ||
+ iph->daddr != whereto.sin_addr.s_addr ||
+ icp1->un.echo.id != getpid())
+ return 1;
+ error_pkt = (icp->type != ICMP_REDIRECT &&
+ icp->type != ICMP_SOURCE_QUENCH);
+ if (error_pkt) {
+ //acknowledge(ntohs(icp1->un.echo.sequence));
+ }
+
+ printf("From %s: icmp_seq=%u ",
+ pr_addr(from->sin_addr.s_addr),
+ ntohs(icp1->un.echo.sequence));
+ if (csfailed)
+ printf("(BAD CHECKSUM)");
+ pr_icmph(icp->type, icp->code, ntohl(icp->un.gateway), icp);
+ return !error_pkt;
+ }
+ default:
+ /* MUST NOT */
+ break;
+ }
+ printf("From %s: ", pr_addr(from->sin_addr.s_addr));
+ pr_icmph(icp->type, icp->code, ntohl(icp->un.gateway), icp);
+ return 0;
+ }
+
+ return 0;
+}
+
+static int read_reply(int icmp_sock, __u8 *packet, int packlen)
+{
+ struct iovec iov;
+ char addrbuf[128];
+ socklen_t addrlen = sizeof(addrbuf);
+ int cc;
+
+ cc = recvfrom(icmp_sock, packet, packlen, 0,
+ (struct sockaddr *) addrbuf, &addrlen);
+ if (cc < 0) {
+ if (errno == EAGAIN || errno == EINTR)
+ return 0;
+ return -1;
+ }
+
+ parse_reply(icmp_sock, packet, cc, addrbuf);
+}
+
+int main(int argc, char **argv)
+{
+ int pmtudisc = IP_PMTUDISC_DO;
+ int yes = 1;
+ int icmp_sock, raw_sock, seq = 0;
+ char *target;
+ struct hostent *hp;
+
+ mtu_size = 1400;
+
+ icmp_sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
+ if (icmp_sock < 0) {
+ perror("mtuinject: socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)");
+ exit(1);
+ }
+
+ if (setsockopt(icmp_sock, SOL_IP, IP_MTU_DISCOVER,
+ &pmtudisc, sizeof(pmtudisc)) == -1) {
+ perror("ping: IP_MTU_DISCOVER");
+ exit(2);
+ }
+
+ if (argc > 1)
+ target = argv[1];
+ else {
+ fprintf(stderr, "usage: %s <host>\n", argv[0]);
+ exit(3);
+ }
+
+ memset((char *)&whereto, 0, sizeof(whereto));
+ whereto.sin_family = AF_INET;
+ if (inet_aton(target, &whereto.sin_addr) != 1) {
+ hp = gethostbyname(target);
+ if (!hp) {
+ fprintf(stderr, "ping: unknown host %s\n", target);
+ exit(2);
+ }
+ memcpy(&whereto.sin_addr, hp->h_addr, 4);
+ }
+
+ printf("Injecting path MTU %d to %s\n",
+ mtu_size - 2, pr_addr(whereto.sin_addr.s_addr));
+ send_probe(icmp_sock, &seq);
+
+ for (;;) {
+ send_probe(icmp_sock, &seq);
+ read_reply(icmp_sock, inpack, sizeof(inpack));
+ sleep(1);
+ }
+}
+
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