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Partial checksum updates for TCP and UDP
This commit is contained in:
parent
88882ea5ca
commit
e35adde820
121
src/checksum.c
121
src/checksum.c
@ -64,6 +64,49 @@ unsigned short checksum(const void *data, int length)
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return ~sum;
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}
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/**
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* General checksum update computation function. Inspired by algorithm
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* in RFC3022.
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*
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* @param old_sum Old checksum
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* @param old_data Pointer to old part of data. Must be of even
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* number of octets
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* @param old_len Length of old data
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* @param new_data Pointer to new part of data. Must be of even
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* number of octets
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* @param new_len Length of new data
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*
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* @return Updated checksum
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*/
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unsigned short checksum_update(unsigned short old_sum,
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unsigned short *old_data, short old_len,
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unsigned short *new_data, short new_len)
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{
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unsigned int sum;
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sum = ~old_sum & 0xffff;
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while (old_len) {
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sum -= *old_data++;
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if (sum & 0x80000000) {
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sum--;
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sum &= 0xffff;
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}
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old_len -= 2;
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}
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while (new_len) {
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sum += *new_data++;
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if (sum & 0x00010000) {
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sum++;
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sum &= 0xffff;
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}
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new_len -= 2;
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}
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return ~sum & 0xffff;
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}
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/**
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* IPv4 checksum computation function
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*
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@ -147,3 +190,81 @@ unsigned short checksum_ipv6(struct s_ipv6_addr ip_src,
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return sum;
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}
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/**
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* IPv4 checksum update computation function
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*
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* @param old_sum Old checksum
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* @param ip6_src Original source IPv6 address
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* @param ip6_dest Original destination IPv6 address
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* @param old_port Original transport layer address (port)
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* @param ip4_src New source IPv4 address
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* @param ip4_dest New destination IPv4 address
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* @param new_port New transport layer address (port)
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*
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* @return Checksum
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*/
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unsigned short checksum_ipv4_update(unsigned short old_sum,
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struct s_ipv6_addr ip6_src,
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struct s_ipv6_addr ip6_dest,
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unsigned short old_port,
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struct s_ipv4_addr ip4_src,
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struct s_ipv4_addr ip4_dest,
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unsigned short new_port)
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{
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struct s_ipv4_pseudo_delta delta4;
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struct s_ipv6_pseudo_delta delta6;
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delta4.ip_src = ip4_src;
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delta4.ip_dest = ip4_dest;
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delta4.port = new_port;
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delta6.ip_src = ip6_src;
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delta6.ip_dest = ip6_dest;
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delta6.port = old_port;
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return checksum_update(old_sum,
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(unsigned short *) &delta6,
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sizeof(struct s_ipv6_pseudo_delta),
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(unsigned short *) &delta4,
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sizeof(struct s_ipv4_pseudo_delta));
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}
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/**
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* IPv6 checksum update computation function
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*
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* @param old_sum Old checksum
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* @param ip4_src Original source IPv4 address
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* @param ip4_dest Original destination IPv4 address
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* @param old_port Original transport layer address (port)
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* @param ip6_src New source IPv6 address
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* @param ip6_dest New destination IPv6 address
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* @param new_port New transport layer address (port)
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*
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* @return Checksum
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*/
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unsigned short checksum_ipv6_update(unsigned short old_sum,
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struct s_ipv4_addr ip4_src,
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struct s_ipv4_addr ip4_dest,
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unsigned short old_port,
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struct s_ipv6_addr ip6_src,
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struct s_ipv6_addr ip6_dest,
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unsigned short new_port)
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{
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struct s_ipv4_pseudo_delta delta4;
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struct s_ipv6_pseudo_delta delta6;
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delta4.ip_src = ip4_src;
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delta4.ip_dest = ip4_dest;
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delta4.port = old_port;
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delta6.ip_src = ip6_src;
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delta6.ip_dest = ip6_dest;
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delta6.port = new_port;
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return checksum_update(old_sum,
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(unsigned short *) &delta4,
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sizeof(struct s_ipv4_pseudo_delta),
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(unsigned short *) &delta6,
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sizeof(struct s_ipv6_pseudo_delta));
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}
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@ -23,11 +23,28 @@
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#include "ipv6.h"
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unsigned short checksum(const void *data, int length);
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unsigned short checksum_update(unsigned short old_sum,
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unsigned short *old_data, short old_len,
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unsigned short *new_data, short new_len);
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unsigned short checksum_ipv4(struct s_ipv4_addr ip_src,
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struct s_ipv4_addr ip_dest, unsigned short length,
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unsigned char proto, unsigned char *payload);
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unsigned short checksum_ipv6(struct s_ipv6_addr ip_src,
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struct s_ipv6_addr ip_dest, unsigned short length,
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unsigned char proto, unsigned char *payload);
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unsigned short checksum_ipv4_update(unsigned short old_sum,
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struct s_ipv6_addr ip6_src,
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struct s_ipv6_addr ip6_dest,
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unsigned short old_port,
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struct s_ipv4_addr ip4_src,
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struct s_ipv4_addr ip4_dest,
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unsigned short new_port);
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unsigned short checksum_ipv6_update(unsigned short old_sum,
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struct s_ipv4_addr ip4_src,
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struct s_ipv4_addr ip4_dest,
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unsigned short old_port,
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struct s_ipv6_addr ip6_src,
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struct s_ipv6_addr ip6_dest,
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unsigned short new_port);
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#endif /* CHECKSUM_H */
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@ -56,6 +56,13 @@ struct s_ipv4_pseudo {
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unsigned short len; /* 16 b; payload length */
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} __attribute__ ((__packed__));
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/* IPv4 pseudoheader structure for checksum update */
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struct s_ipv4_pseudo_delta {
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struct s_ipv4_addr ip_src; /* 32 b; source address */
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struct s_ipv4_addr ip_dest; /* 32 b; destination address */
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unsigned short port; /* 16 b; transport layer address */
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} __attribute__ ((__packed__));
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int ipv4(struct s_ethernet *eth, char *packet);
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#endif /* IPV4_H */
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@ -47,6 +47,13 @@ struct s_ipv6_pseudo {
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unsigned char next_header; /* 8 b; next header */
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} __attribute__ ((__packed__));
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/* IPv6 pseudoheader structure for checksum update */
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struct s_ipv6_pseudo_delta {
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struct s_ipv6_addr ip_src; /* 128 b; source address */
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struct s_ipv6_addr ip_dest; /* 128 b; destination address */
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unsigned short port; /* 16 b; transport layer address */
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} __attribute__ ((__packed__));
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int ipv6(struct s_ethernet *eth, char *packet);
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#endif /* IPV6_H */
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17
src/tcp.c
17
src/tcp.c
@ -110,9 +110,11 @@ int tcp_ipv4(struct s_ethernet *eth, struct s_ipv4 *ip4, char *payload,
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tcp->port_dest = connection->ipv6_port_src;
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/* compute TCP checksum */
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tcp->checksum = 0x0;
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tcp->checksum = checksum_ipv6(ip6->ip_src, ip6->ip_dest, payload_size,
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IPPROTO_TCP, (unsigned char *) tcp);
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tcp->checksum = checksum_ipv6_update(tcp->checksum,
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ip4->ip_src, ip4->ip_dest,
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connection->ipv4_port_src,
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ip6->ip_src, ip6->ip_dest,
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connection->ipv6_port_src);
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/* copy the payload data (with new checksum) */
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memcpy(packet + sizeof(struct s_ethernet) + sizeof(struct s_ipv6),
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@ -198,10 +200,11 @@ int tcp_ipv6(struct s_ethernet *eth, struct s_ipv6 *ip6, char *payload)
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tcp->port_src = connection->ipv4_port_src;
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/* compute TCP checksum */
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tcp->checksum = 0;
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tcp->checksum = checksum_ipv4(ip4->ip_src, ip4->ip_dest,
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htons(ip6->len), IPPROTO_TCP,
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(unsigned char *) tcp);
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tcp->checksum = checksum_ipv4_update(tcp->checksum,
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ip6->ip_src, ip6->ip_dest,
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connection->ipv6_port_src,
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ip4->ip_src, ip4->ip_dest,
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connection->ipv4_port_src);
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/* copy the payload data (with new checksum) */
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memcpy(packet + sizeof(struct s_ipv4), payload, htons(ip6->len));
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23
src/udp.c
23
src/udp.c
@ -110,9 +110,17 @@ int udp_ipv4(struct s_ethernet *eth, struct s_ipv4 *ip4, char *payload,
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udp->port_dest = connection->ipv6_port_src;
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/* compute UDP checksum */
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udp->checksum = 0x0;
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udp->checksum = checksum_ipv6(ip6->ip_src, ip6->ip_dest, payload_size,
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IPPROTO_UDP, (unsigned char *) udp);
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if (udp->checksum) {
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udp->checksum = checksum_ipv6_update(udp->checksum,
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ip4->ip_src, ip4->ip_dest,
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connection->ipv4_port_src,
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ip6->ip_src, ip6->ip_dest,
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connection->ipv6_port_src);
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} else {
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/* if original checksum was 0x0000, we need to compute it */
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udp->checksum = checksum_ipv6(ip6->ip_src, ip6->ip_dest, payload_size,
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IPPROTO_UDP, (unsigned char *) udp);
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}
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/* copy the payload data (with new checksum) */
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memcpy(packet + sizeof(struct s_ethernet) + sizeof(struct s_ipv6),
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@ -198,10 +206,11 @@ int udp_ipv6(struct s_ethernet *eth, struct s_ipv6 *ip6, char *payload)
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udp->port_src = connection->ipv4_port_src;
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/* compute UDP checksum */
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udp->checksum = 0x0;
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udp->checksum = checksum_ipv4(ip4->ip_src, ip4->ip_dest,
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htons(ip6->len), IPPROTO_UDP,
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(unsigned char *) payload);
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udp->checksum = checksum_ipv4_update(udp->checksum,
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ip6->ip_src, ip6->ip_dest,
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connection->ipv6_port_src,
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ip4->ip_src, ip4->ip_dest,
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connection->ipv4_port_src);
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/* copy the payload data (with new checksum) */
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memcpy(packet + sizeof(struct s_ipv4), payload, htons(ip6->len));
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