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Finish cleaning up get_raw_packet(). Use offsetof() to make UDP

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checksum verification a bit more compact.
This commit is contained in:
Nicholas J. Kain 2010-11-13 08:47:07 -05:00
parent 693c9256e4
commit 71a3603934
1 changed files with 6 additions and 12 deletions
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18
ndhc/clientpacket.c
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@ -181,7 +181,6 @@ int send_release(uint32_t server, uint32_t ciaddr)
int get_raw_packet(struct dhcpMessage *payload, int fd) int get_raw_packet(struct dhcpMessage *payload, int fd)
{ {
struct udp_dhcp_packet packet; struct udp_dhcp_packet packet;
uint32_t source, dest;
uint16_t check; uint16_t check;
const int header_size = sizeof(struct iphdr) + sizeof(struct udphdr); const int header_size = sizeof(struct iphdr) + sizeof(struct udphdr);
const int packet_size = sizeof(struct udp_dhcp_packet); const int packet_size = sizeof(struct udp_dhcp_packet);
@ -245,23 +244,18 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
check = packet.ip.check; check = packet.ip.check;
packet.ip.check = 0; packet.ip.check = 0;
if (check != checksum(&packet.ip, sizeof packet.ip)) { if (check != checksum(&packet.ip, sizeof packet.ip)) {
log_line("bad IP header checksum, ignoring"); log_line("Bad IP header checksum, ignoring");
return -1; return -1;
} }
/* verify the UDP checksum by replacing the header with a psuedo header */ /* verify the UDP checksum by replacing the header with a psuedo header */
source = packet.ip.saddr; memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
dest = packet.ip.daddr; /* preserved fields: protocol, check, saddr, daddr */
packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
check = packet.udp.check; check = packet.udp.check;
packet.udp.check = 0; packet.udp.check = 0;
memset(&packet.ip, 0, sizeof packet.ip);
packet.ip.protocol = IPPROTO_UDP;
packet.ip.saddr = source;
packet.ip.daddr = dest;
packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
if (check && check != checksum(&packet, len)) { if (check && check != checksum(&packet, len)) {
log_error("packet with bad UDP checksum received, ignoring"); log_error("Packet with bad UDP checksum received, ignoring");
return -2; return -2;
} }
@ -269,7 +263,7 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
len - sizeof packet.ip - sizeof packet.udp); len - sizeof packet.ip - sizeof packet.udp);
if (ntohl(payload->cookie) != DHCP_MAGIC) { if (ntohl(payload->cookie) != DHCP_MAGIC) {
log_error("received bogus message (bad magic) -- ignoring"); log_error("Packet with bad magic number, ignoring");
return -2; return -2;
} }
log_line("Received valid DHCP message."); log_line("Received valid DHCP message.");