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Some improvements, fix compiler warnings #35

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9cd7472
test: l4_sum() function
rpoisel Jan 18, 2022
a1c832e
fix: l4_sum function
rpoisel Jan 18, 2022
b6ce853
chore: fix compiler warnings
rpoisel Jan 18, 2022
9efe6b4
fix: one more compiler warning
rpoisel Jan 20, 2022
dc926e5
chore: gitignore some more LSP files
rpoisel Jan 20, 2022
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3 changes: 3 additions & 0 deletions .gitignore
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Expand Up @@ -2,3 +2,6 @@ dhtest
*.o
00:*
dhscript_log.txt
compile_commands.json
chksum_test
.cache/
21 changes: 16 additions & 5 deletions Makefile
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@@ -1,10 +1,21 @@
# Makefile to generate dhtest

CC=gcc
#CFLAGS=-Wall -g
CC = gcc
CFLAGS ?= -Wall -Wextra

dhtest: dhtest.o functions.o
$(CC) $(LDFLAGS) dhtest.o functions.o -o dhtest
dhtest: dhtest.o functions.o chksum.o
$(CC) $(LDFLAGS) $^ -o dhtest

chksum_test: chksum.o functions_test.o dhcp_err.o
$(CC) $(LDFLAGS) $^ -o chksum_test

.PHONY: test
test: chksum_test
./chksum_test

.PHONY: debug
debug: chksum_test
gdb --args ./chksum_test

clean:
rm -f dhtest functions.o dhtest.o
rm -f dhtest chksum_test *.o
35 changes: 35 additions & 0 deletions chksum.c
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@@ -0,0 +1,35 @@
#include "chksum.h"

#include <arpa/inet.h>

#include <stdint.h>
#include <stdio.h>

/*
* TCP/UDP checksum function, RFC 768
*/
u_int16_t l4_sum(u_int16_t *buff, int words, u_int32_t *srcaddr, u_int32_t *dstaddr, u_int16_t proto, u_int16_t len)
{
unsigned int last_word;

/* Checksum enhancement - Support for odd byte packets */
if((htons(len) % 2) == 1) {
last_word = *((u_int8_t *)buff + ntohs(len) - 1);
last_word = htons(last_word << 8);
} else {
/* Original checksum function */
last_word = 0;
}

uint32_t sum = 0;
for(int i = 0; i < words; i++){
sum = sum + *(buff + i);
}

sum = sum + last_word;
/* pseudo IPv4 header */
sum = sum + (*(srcaddr) & 0xffff) + (*(srcaddr) >> 16) + (*(dstaddr) & 0xffff) + (*(dstaddr) >> 16) + proto + len;
/* carry-out bits */
sum = (sum >> 16) + sum;
return ~sum;
}
8 changes: 8 additions & 0 deletions chksum.h
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@@ -0,0 +1,8 @@
#ifndef CHKSUM_H
#define CHKSUM_H

#include<sys/types.h>

u_int16_t l4_sum(u_int16_t *buff, int words, u_int32_t *srcaddr, u_int32_t *dstaddr, u_int16_t proto, u_int16_t len);

#endif /* CHKSUM_H */
40 changes: 40 additions & 0 deletions dhcp_err.c
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@@ -0,0 +1,40 @@
/* Frame (305 bytes) */
const unsigned char pkt410[271] = {
0x00, 0x44, 0x00, 0x43, 0x01, 0x0f, /* .D.C.. */
/* 0x1d, 0xff, 0x01, 0x01, 0x06, 0x00, 0x2b, 0x01, */ /* ......+. */
0x00, 0x00, 0x01, 0x01, 0x06, 0x00, 0x2b, 0x01, /* ......+. */
0xd8, 0x97, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x42, 0x00, /* ......B. */
0x05, 0x01, 0x00, 0xcc, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ........ */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x63, 0x82, /* ......c. */
0x53, 0x63, 0x35, 0x01, 0x03, 0x32, 0x04, 0x0a, /* Sc5..2.. */
0x00, 0x72, 0x43, 0x36, 0x04, 0xac, 0x10, 0x2a, /* .rC6...* */
0x13, 0x37, 0x05, 0x01, 0x1c, 0x03, 0x0f, 0x06, /* .7...... */
0xff /* . */
};

6 changes: 6 additions & 0 deletions dhcp_err.h
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@@ -0,0 +1,6 @@
#ifndef DHCP_ERR_H
#define DHCP_ERR_H

extern const unsigned char pkt410[271];

#endif /* DHCP_ERR_H */
4 changes: 2 additions & 2 deletions dhtest.c
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Expand Up @@ -306,8 +306,8 @@ int main(int argc, char *argv[])
}
u_int32_t hex_length = (strlen((const char *) option55_req_list_tmp)/2);

int tmp, index = 0;
for(tmp = 0; tmp < hex_length; tmp++) {
int index = 0;
for(u_int32_t tmp = 0; tmp < hex_length; tmp++) {
sscanf(&option55_req_list_tmp[index], "%2X", (unsigned int*)&option55_req_list[tmp]);
index = index + 2;
}
Expand Down
51 changes: 12 additions & 39 deletions functions.c
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Expand Up @@ -14,6 +14,7 @@
#include<linux/if_ether.h>
#include<linux/if_arp.h>
#include "headers.h"
#include "chksum.h"

//Defined in dhtest.c
extern int sock_packet;
Expand Down Expand Up @@ -539,9 +540,9 @@ int set_rand_dhcp_xid()
*/
u_int16_t ipchksum(u_int16_t *buff, int words)
{
unsigned int sum, i;
unsigned int sum;
sum = 0;
for(i = 0;i < words; i++){
for(int i = 0;i < words; i++){
sum = sum + *(buff + i);
}
sum = (sum >> 16) + sum;
Expand All @@ -553,56 +554,29 @@ u_int16_t ipchksum(u_int16_t *buff, int words)
*/
u_int16_t icmpchksum(u_int16_t *buff, int words)
{
unsigned int sum, i;
unsigned int sum;
unsigned int last_word = 0;
/* Checksum enhancement for odd packets */
if((icmp_len % 2) == 1) {
last_word = *((u_int8_t *)buff + icmp_len + ICMP_H - 1);
last_word = (htons(last_word) << 8);
sum = 0;
for(i = 0;i < words; i++){
for(int i = 0;i < words; i++){
sum = sum + *(buff + i);
}
sum = sum + last_word;
sum = (sum >> 16) + sum;
return (u_int16_t)~sum;
} else {
sum = 0;
for(i = 0;i < words; i++){
for(int i = 0;i < words; i++){
sum = sum + *(buff + i);
}
sum = (sum >> 16) + sum;
return (u_int16_t)~sum;
}
}

/*
* TCP/UDP checksum function
*/
u_int16_t l4_sum(u_int16_t *buff, int words, u_int16_t *srcaddr, u_int16_t *dstaddr, u_int16_t proto, u_int16_t len)
{
unsigned int i, last_word;
uint32_t sum;

/* Checksum enhancement - Support for odd byte packets */
if((htons(len) % 2) == 1) {
last_word = *((u_int8_t *)buff + ntohs(len) - 1);
last_word = (htons(last_word) << 8);
} else {
/* Original checksum function */
last_word = 0;
}

sum = 0;
for(i = 0;i < words; i++){
sum = sum + *(buff + i);
}
sum = sum + last_word;
sum = sum + *(srcaddr) + *(srcaddr + 1) + *(dstaddr) + *(dstaddr + 1) + proto + len;
sum = (sum >> 16) + sum;
return ~sum;
}

/*
* Builds DHCP option53 on dhopt_buff
*/
Expand Down Expand Up @@ -674,7 +648,7 @@ int build_option54()
/*
* Builds DHCP option55 on dhopt_buff
*/
int build_option55()
void build_option55()
{
if (option55_req_flag == 0) {
u_int32_t msgtype = DHCP_PARAMREQUEST;
Expand All @@ -691,7 +665,6 @@ int build_option55()
memcpy((dhopt_buff + dhopt_size + 1), &msglen, 1);
memcpy((dhopt_buff + dhopt_size + 2), msg, 5);
dhopt_size = dhopt_size + 7;
return 0;
} else if (option55_req_flag == 1) {
u_int32_t msgtype = DHCP_PARAMREQUEST;
u_int32_t msglen = option55_req_len;
Expand Down Expand Up @@ -889,7 +862,7 @@ int build_dhpacket(int pkt_type)
memcpy(dhopt_pointer, dhopt_buff, dhopt_size);

/* UDP checksum is done here */
uh->check = l4_sum((u_int16_t *) (dhcp_packet_disc + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), (u_int16_t *)&iph->saddr, (u_int16_t *)&iph->daddr, htons(l4_proto), htons(l4_len));
uh->check = l4_sum((u_int16_t *) (dhcp_packet_disc + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), &iph->saddr, &iph->daddr, htons(l4_proto), htons(l4_len));
}
if(pkt_type == DHCP_MSGREQUEST) {
if(vlan == 0) {
Expand Down Expand Up @@ -962,7 +935,7 @@ int build_dhpacket(int pkt_type)
memcpy(dhopt_pointer, dhopt_buff, dhopt_size);

/* UDP checksum is done here */
uh->check = l4_sum((u_int16_t *) (dhcp_packet_request + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), (u_int16_t *)&iph->saddr, (u_int16_t *)&iph->daddr, htons(l4_proto), htons(l4_len));
uh->check = l4_sum((u_int16_t *) (dhcp_packet_request + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), &iph->saddr, &iph->daddr, htons(l4_proto), htons(l4_len));
}
if(pkt_type == DHCP_MSGRELEASE) {
if(vlan == 0) {
Expand Down Expand Up @@ -1025,11 +998,11 @@ int build_dhpacket(int pkt_type)
dhpointer->dhcp_magic = htonl(DHCP_MAGIC);

/* DHCP option buffer is copied here to DHCP packet */
u_char *dhopt_pointer = (u_char *)(dhcp_packet_release + l2_hdr_size + l3_hdr_size + l4_hdr_size + dhcp_hdr_size);
u_char *dhopt_pointer = dhcp_packet_release + l2_hdr_size + l3_hdr_size + l4_hdr_size + dhcp_hdr_size;
memcpy(dhopt_pointer, dhopt_buff, dhopt_size);

/* UDP checksum is done here */
uh->check = l4_sum((u_int16_t *) (dhcp_packet_release + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), (u_int16_t *)&iph->saddr, (u_int16_t *)&iph->daddr, htons(l4_proto), htons(l4_len));
uh->check = l4_sum((u_int16_t *) (dhcp_packet_release + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), &iph->saddr, &iph->daddr, htons(l4_proto), htons(l4_len));
}

if(pkt_type == DHCP_MSGDECLINE) {
Expand Down Expand Up @@ -1096,7 +1069,7 @@ int build_dhpacket(int pkt_type)
memcpy(dhopt_pointer, dhopt_buff, dhopt_size);

/* UDP checksum is done here */
uh->check = l4_sum((u_int16_t *) (dhcp_packet_decline + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), (u_int16_t *)&iph->saddr, (u_int16_t *)&iph->daddr, htons(l4_proto), htons(l4_len));
uh->check = l4_sum((u_int16_t *) (dhcp_packet_decline + l2_hdr_size + l3_hdr_size), ((dhcp_hdr_size + dhopt_size + l4_hdr_size) / 2), &iph->saddr, &iph->daddr, htons(l4_proto), htons(l4_len));
}

return 0;
Expand Down
14 changes: 14 additions & 0 deletions functions_test.c
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@@ -0,0 +1,14 @@
#include "chksum.h"
#include "dhcp_err.h"

#include <arpa/inet.h>

#include <stdio.h>

int main(void) {
uint32_t srcaddr = 0x0;
uint32_t dstaddr = 0xffffffff;

printf("0x%X\n", l4_sum((u_int16_t*)&pkt410[0], sizeof(pkt410) / 2, &srcaddr, &dstaddr, htons(17), htons(sizeof(pkt410))));
return 0;
}
7 changes: 5 additions & 2 deletions headers.h
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Expand Up @@ -22,7 +22,7 @@ int recv_packet(int pkt_type); /* Receives DHCP packet on socket*/
int reset_dhopt_size(); /* Resets the dhopt_size to zero */
int set_rand_dhcp_xid(); /* Sets a random DHCP xid */
int build_option53(int msg_type); /* Option53: MSGTYPE. Builds option53*/
int build_option55(); /* Requested parameters list */
void build_option55(); /* Requested parameters list */
int build_option54(); /* Builds server identifier on DHCP request */
int build_option50(); /* Option50: Rqstd IP. Builds option50*/
int build_option51(); /* Option51: Rqstd lease time. Builds option51*/
Expand Down Expand Up @@ -153,8 +153,11 @@ struct icmp_hdr
/*
* UDP header included from netinet/udp.h
*/
#if 0
#include<netinet/udp.h>

#else
#include<linux/udp.h>
#endif

/*
* DHCP header
Expand Down