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-rw-r--r--client.c12
-rw-r--r--icmp.c119
-rw-r--r--icmp.h20
-rw-r--r--icmp_client.h23
-rw-r--r--icmp_server.h32
-rwxr-xr-xrun_server.sh12
-rw-r--r--server.c107
7 files changed, 184 insertions, 141 deletions
diff --git a/client.c b/client.c
index 1f8663f..4c1a32f 100644
--- a/client.c
+++ b/client.c
@@ -6,22 +6,24 @@
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>
#include <unistd.h>
-#include "icmp.h"
+#include "icmp_client.h"
#include "util.h"
int main(void) {
- int sock = icmp_open_socket();
+ int sock = icmp_client_open_socket();
if (sock < 0) {
- perror("icmp_open_socket");
+ perror("icmp_client_open_socket");
return 1;
}
const char *ip_address = "127.0.0.1";
// const char *ip_address = "192.168.43.220";
+ // const char *ip_address = "198.211.118.67"; // tomsmeding.com
- struct icmp_reply reply = icmp_communicate(sock, ip_address, 1234, "kaashandel", 10);
+ struct icmp_client_incoming reply =
+ icmp_client_communicate(sock, ip_address, 42, 1234, "kaashandel", 10);
if (reply.data == NULL) {
- perror("icmp_communicate");
+ perror("icmp_client_communicate");
return 1;
}
diff --git a/icmp.c b/icmp.c
index 63436ac..bef1fd6 100644
--- a/icmp.c
+++ b/icmp.c
@@ -1,24 +1,28 @@
#include <stdlib.h>
+#include <stdbool.h>
#include <stddef.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
+#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>
-#include "icmp.h"
+#include "icmp_client.h"
+#include "icmp_server.h"
#include "util.h"
-#define PROT_ICMP 1
-
-
-static void make_sockaddr(struct sockaddr_in *dst, const char *ip_address) {
+static void make_sockaddr_u32(struct sockaddr_in *dst, uint32_t addr) {
memset(dst, 0, sizeof *dst);
dst->sin_family = AF_INET;
dst->sin_port = htons(0);
- dst->sin_addr.s_addr = inet_addr(ip_address);
+ dst->sin_addr.s_addr = addr;
+}
+
+static void make_sockaddr(struct sockaddr_in *dst, const char *ip_address) {
+ make_sockaddr_u32(dst, inet_addr(ip_address));
}
static uint16_t compute_checksum(const void *buf_, size_t buflen) {
@@ -39,18 +43,27 @@ static uint16_t compute_checksum(const void *buf_, size_t buflen) {
return res;
}
-int icmp_open_socket(void) {
- return socket(PF_INET, SOCK_DGRAM, PROT_ICMP);
+int icmp_client_open_socket(void) {
+ return socket(PF_INET, SOCK_DGRAM, IPPROTO_ICMP);
}
-struct icmp_reply icmp_communicate(int sock, const char *ip_address, int seqnum, const void *data_, size_t length) {
+int icmp_server_open_socket(void) {
+ return socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
+}
+
+struct icmp_client_incoming icmp_client_communicate(
+ int sock, const char *ip_address,
+ int id, int seqnum,
+ const void *data_, size_t length) {
+
static uint8_t buffer[ICMP_MAX_PAYLOAD_LENGTH];
const uint8_t *data = (const uint8_t*)data_;
assert(length <= ICMP_MAX_PAYLOAD_LENGTH);
- struct icmp_reply errret = (struct icmp_reply){.data = NULL, .length = 0, .seqnum = 0};
+ struct icmp_client_incoming errret =
+ (struct icmp_client_incoming){.data = NULL, .length = 0, .id = 0, .seqnum = 0};
struct sockaddr_in addr;
make_sockaddr(&addr, ip_address);
@@ -59,7 +72,8 @@ struct icmp_reply icmp_communicate(int sock, const char *ip_address, int seqnum,
memset(&msg, 0, sizeof msg);
msg.type = ICMP_ECHO;
msg.code = 0;
- msg.seqnum = seqnum;
+ msg.id = htons(id);
+ msg.seqnum = htons(seqnum);
memcpy(msg.payload, data, length);
@@ -90,25 +104,90 @@ struct icmp_reply icmp_communicate(int sock, const char *ip_address, int seqnum,
memcpy(buffer, msg.payload, payloadlen);
- return (struct icmp_reply){
+ return (struct icmp_client_incoming){
.data = buffer,
.length = payloadlen,
- .seqnum = msg.seqnum
+ .id = ntohs(msg.id),
+ .seqnum = ntohs(msg.seqnum)
};
}
-int icmp_send_echo_reply(const char *ip_address, int id, int seqnum, const void *data_, size_t length) {
+struct icmp_server_incoming icmp_server_receive(int sock) {
+ static uint8_t buffer[ICMP_MAX_PAYLOAD_LENGTH];
+
+ struct icmp_server_incoming errret =
+ (struct icmp_server_incoming){.data = NULL, .length = 0, .id = 0, .seqnum = 0, .source_addr = 0};
+
+ char buf[MAX_IP_PACKET_SIZE];
+
+ struct iovec iov1;
+ memset(&iov1, 0, sizeof iov1);
+ iov1.iov_base = buf;
+ iov1.iov_len = sizeof buf;
+
+ struct msghdr recv_msghdr;
+ memset(&recv_msghdr, 0, sizeof recv_msghdr);
+ recv_msghdr.msg_name = NULL;
+ recv_msghdr.msg_iov = &iov1;
+ recv_msghdr.msg_iovlen = 1;
+
+ // TODO: check whether the above stuff needs re-initialisation
+ while (true) {
+ recv_msghdr.msg_flags = 0;
+
+ ssize_t nr = recvmsg(sock, &recv_msghdr, 0);
+ if (nr < 0) return errret;
+
+ // buf now contains received data starting at the IP header
+
+ // printf("Full packet received:\n");
+ // xxd(buf, nr);
+
+ struct iphdr *hdr = (struct iphdr*)buf;
+ int hdr_len = hdr->ihl * 4;
+ uint32_t saddr = hdr->saddr;
+
+ struct icmp_echo *msg = (struct icmp_echo*)(buf + hdr_len);
+ int msg_len = nr - hdr_len;
+ int payloadlen = msg_len - offsetof(struct icmp_echo, payload);
+ // printf("Received: type %u code %u id %hu seqnum %hu payload:\n",
+ // (unsigned)msg->type, (unsigned)msg->code, msg->id, msg->seqnum);
+ // xxd(msg->payload, payloadlen);
+
+ if (msg->type != ICMP_ECHO && msg->type != ICMP_ECHOREPLY) {
+ // printf("Not an ICMP_ECHO or ICMP_ECHOREPLY, ignoring\n");
+ continue;
+ } else {
+ memcpy(buffer, msg->payload, payloadlen);
+
+ return (struct icmp_server_incoming){
+ .data = buffer,
+ .length = payloadlen,
+ .type = msg->type,
+ .id = ntohs(msg->id),
+ .seqnum = ntohs(msg->seqnum),
+ .source_addr = saddr
+ };
+ }
+ }
+}
+
+int icmp_server_send_reply(
+ int sock, uint32_t addr_u32,
+ int id, int seqnum,
+ const void *data_, size_t length) {
+
const uint8_t *data = (const uint8_t*)data_;
struct sockaddr_in addr;
- make_sockaddr(&addr, ip_address);
+ make_sockaddr_u32(&addr, addr_u32);
struct icmp_echo msg;
memset(&msg, 0, sizeof msg);
msg.type = ICMP_ECHOREPLY;
msg.code = 0;
- msg.id = id;
- msg.seqnum = seqnum;
+ msg.id = htons(id);
+ msg.seqnum = htons(seqnum);
msg.checksum = 0;
memcpy(msg.payload, data, length);
@@ -117,13 +196,7 @@ int icmp_send_echo_reply(const char *ip_address, int id, int seqnum, const void
msg.checksum = ~compute_checksum(&msg, total_length);
- int sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
- // The below is only necessary for sending on IPPROTO_RAW sockets
- // int zero = 0;
- // assert(setsockopt(sock, IPPROTO_IP, IP_HDRINCL, &zero, sizeof zero) >= 0);
-
int ret = sendto(sock, &msg, ICMP_PAYLOAD_OFFSET + length, 0, (struct sockaddr*)&addr, sizeof addr);
- close(sock);
if (ret < 0) return -1;
return 0;
diff --git a/icmp.h b/icmp.h
index 3557fc3..4cccb95 100644
--- a/icmp.h
+++ b/icmp.h
@@ -22,23 +22,3 @@ struct __attribute__((packed)) icmp_echo {
#define ICMP_MAX_PAYLOAD_LENGTH (MAX_DATAGRAM_SIZE - ICMP_PAYLOAD_OFFSET)
#define ICMP_SAFE_PAYLOAD_LENGTH (MIN_MTU - IP_HEADER_SIZE - ICMP_PAYLOAD_OFFSET)
-
-
-struct icmp_reply {
- const uint8_t *data; // points to internal buffer
- size_t length; // length of 'data'
-
- int seqnum;
-};
-
-// Returns -1 on error with errno.
-int icmp_open_socket(void);
-
-// Only actual IPv4 addresses allowed. Sends data in 'data' with length 'length', and
-// returns pointer to internal buffer with reply data. Buffer is invalidated on next
-// call to the function.
-// Returns {.data=NULL} on error with errno.
-struct icmp_reply icmp_communicate(int sock, const char *ip_address, int seqnum, const void *data, size_t length);
-
-// Returns -1 on error with errno.
-int icmp_send_echo_reply(const char *ip_address, int id, int seqnum, const void *data, size_t length);
diff --git a/icmp_client.h b/icmp_client.h
new file mode 100644
index 0000000..78cfe7a
--- /dev/null
+++ b/icmp_client.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include "icmp.h"
+
+
+struct icmp_client_incoming {
+ const uint8_t *data; // points to internal buffer
+ size_t length; // length of 'data'
+
+ int id, seqnum;
+};
+
+// Returns -1 on error with errno.
+int icmp_client_open_socket(void);
+
+// Only actual IPv4 addresses allowed. Sends data in 'data' with length 'length', and
+// returns pointer to internal buffer with reply data. Buffer is invalidated on next
+// call to the function.
+// Returns {.data=NULL} on error with errno.
+struct icmp_client_incoming icmp_client_communicate(
+ int sock, const char *ip_address,
+ int id, int seqnum,
+ const void *data, size_t length);
diff --git a/icmp_server.h b/icmp_server.h
new file mode 100644
index 0000000..fbf4158
--- /dev/null
+++ b/icmp_server.h
@@ -0,0 +1,32 @@
+#pragma once
+
+#include "icmp.h"
+
+#ifndef ICMP_ECHO
+#define ICMP_ECHO 8
+#endif
+#ifndef ICMP_ECHOREPLY
+#define ICMP_ECHOREPLY 0
+#endif
+
+
+struct icmp_server_incoming {
+ const uint8_t *data; // points to internal buffer
+ size_t length; // length of 'data'
+
+ int type; // ICMP_ECHO or ICMP_ECHOREPLY
+ int id, seqnum;
+ uint32_t source_addr;
+};
+
+// Returns -1 on error with errno.
+int icmp_server_open_socket(void);
+
+// Returns {.data=NULL} on error with errno.
+struct icmp_server_incoming icmp_server_receive(int sock);
+
+// Returns -1 on error with errno.
+int icmp_server_send_reply(
+ int sock, uint32_t addr,
+ int id, int seqnum,
+ const void *data, size_t length);
diff --git a/run_server.sh b/run_server.sh
index 50764b1..42b6aef 100755
--- a/run_server.sh
+++ b/run_server.sh
@@ -1,5 +1,9 @@
#!/usr/bin/env bash
-sudo -v
-echo 1 | sudo tee /proc/sys/net/ipv4/icmp_echo_ignore_all
-sudo ./server
-echo 0 | sudo tee /proc/sys/net/ipv4/icmp_echo_ignore_all
+if [[ "$(id -u)" -ne 0 ]]; then
+ echo >&2 "Run with sudo"
+ exit 1
+fi
+
+echo 1 >/proc/sys/net/ipv4/icmp_echo_ignore_all
+trap "echo 0 >/proc/sys/net/ipv4/icmp_echo_ignore_all" EXIT
+./server
diff --git a/server.c b/server.c
index db269e5..9b16173 100644
--- a/server.c
+++ b/server.c
@@ -1,108 +1,37 @@
#include <stdio.h>
#include <stdbool.h>
-#include <stddef.h>
#include <stdlib.h>
-#include <string.h>
#include <unistd.h>
-#include <stdint.h>
-#include <arpa/inet.h>
-#include <netinet/ip.h>
-#include <netinet/ip_icmp.h>
-#include "icmp.h"
+#include "icmp_server.h"
#include "util.h"
-struct state {
- int socket;
-};
-
-#if 0
-static int icmp_callback(struct nflog_data *ldata, void *state_) {
- (void)gh; (void)nfmsg;
-
- struct state *state = (struct state*)state_;
-
- uint8_t *ip_start; // received packet, starting at the IP buffer
- int ip_len = nflog_get_payload(ldata, (char**)&ip_start);
-
- struct iphdr *hdr = (struct iphdr*)ip_start;
- int hdr_len = hdr->ihl * 4;
- uint32_t saddr = hdr->saddr;
-
- struct icmp_echo *msg = (struct icmp_echo*)(ip_start + hdr_len);
- int msg_len = ip_len - hdr_len;
- printf("Received: type %u code %u id %hu seqnum %hu payload:\n",
- (unsigned)msg->type, (unsigned)msg->code, msg->id, msg->seqnum);
- xxd(msg->payload, msg_len - offsetof(struct icmp_echo, payload));
-
- uint8_t *saddr_bytes = (uint8_t*)&saddr;
- char ip_address[16];
- sprintf(ip_address, "%u.%u.%u.%u", saddr_bytes[0], saddr_bytes[1], saddr_bytes[2], saddr_bytes[3]);
- if (icmp_send_echo_reply(ip_address, msg->id, msg->seqnum, "dank je wel", 11) < 0) {
- perror("icmp_send_echo_reply");
- }
-
- return 0;
-}
-#endif
-
-
int main(void) {
- // struct state state;
- // state.socket = icmp_open_socket();
- // if (state.socket < 0) {
- // perror("icmp_open_socket");
- // return 1;
- // }
-
- int sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
-
- struct icmp_echo msg;
+ int sock = icmp_server_open_socket();
+ if (sock < 0) {
+ perror("icmp_server_open_socket");
+ return 1;
+ }
- char buf[MAX_IP_PACKET_SIZE];
while (true) {
- struct iovec iov1;
- memset(&iov1, 0, sizeof iov1);
- iov1.iov_base = buf;
- iov1.iov_len = sizeof buf;
-
- struct sockaddr_in addr;
-
- struct msghdr recv_msghdr;
- memset(&recv_msghdr, 0, sizeof recv_msghdr);
- recv_msghdr.msg_name = &addr;
- recv_msghdr.msg_namelen = sizeof addr;
- recv_msghdr.msg_iov = &iov1;
- recv_msghdr.msg_iovlen = 1;
-
- ssize_t nr = recvmsg(sock, &recv_msghdr, 0);
- if (nr < 0) break;
-
- // buf now contains received data starting at the IP header
-
- printf("Full packet received:\n");
- xxd(buf, nr);
-
- struct iphdr *hdr = (struct iphdr*)buf;
- int hdr_len = hdr->ihl * 4;
- uint32_t saddr = hdr->saddr;
+ struct icmp_server_incoming msg = icmp_server_receive(sock);
+ if (msg.data == NULL) {
+ perror("icmp_server_communicate");
+ return 1;
+ }
- struct icmp_echo *msg = (struct icmp_echo*)(buf + hdr_len);
- int msg_len = nr - hdr_len;
- printf("Received: type %u code %u id %hu seqnum %hu payload:\n",
- (unsigned)msg->type, (unsigned)msg->code, msg->id, msg->seqnum);
- xxd(msg->payload, msg_len - offsetof(struct icmp_echo, payload));
+ printf("Received: type %d id %d seqnum %d data:\n", msg.type, msg.id, msg.seqnum);
+ xxd(msg.data, msg.length);
- if (msg->type != ICMP_ECHO) {
+ if (msg.type != ICMP_ECHO) {
printf("Not an ICMP_ECHO, ignoring\n");
continue;
}
- uint8_t *saddr_bytes = (uint8_t*)&saddr;
- char ip_address[16];
- sprintf(ip_address, "%u.%u.%u.%u", saddr_bytes[0], saddr_bytes[1], saddr_bytes[2], saddr_bytes[3]);
- if (icmp_send_echo_reply(ip_address, msg->id, msg->seqnum, "dank je wel", 11) < 0) {
- perror("icmp_send_echo_reply");
+ if (icmp_server_send_reply(sock, msg.source_addr, msg.id, msg.seqnum, "dank je wel", 11) < 0) {
+ perror("icmp_server_send_reply");
}
}
+
+ close(sock);
}
generated by cgit v1.2.3-70-g09d2 (git 2.47.0) at 2024-12-05 03:42:29 +0100