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Patch by Andrew Victor,

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In arpping.h, fix structure alignment of "struct arpMsg".
GCC can insert padding in the structure which causes udhcpd to send an
invalid ARP packet on the network.  It will then not receive a valid
reply, which can cause it to assign an IP address that's already in use
on the network.
(With kernels before 2.4.20, the "struct ethhdr" in linux/if_ether.h
wasn't marked as packed.  This is also an issue if your toolchain was
built with a pre-2.4.20 kernel).
This commit is contained in:
Glenn L McGrath 2004-03-05 14:25:49 +00:00
parent 0226596dcb
commit 3f79300e37
2 changed files with 10 additions and 5 deletions
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6
networking/udhcp/arpping.c
View File

@ -60,9 +60,9 @@ int arpping(uint32_t yiaddr, uint32_t ip, uint8_t *mac, char *interface)
/* send arp request */
memset(&arp, 0, sizeof(arp));
memcpy(arp.ethhdr.h_dest, MAC_BCAST_ADDR, 6); /* MAC DA */
memcpy(arp.ethhdr.h_source, mac, 6); /* MAC SA */
arp.ethhdr.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */
memcpy(arp.h_dest, MAC_BCAST_ADDR, 6); /* MAC DA */
memcpy(arp.h_source, mac, 6); /* MAC SA */
arp.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */
arp.htype = htons(ARPHRD_ETHER); /* hardware type */
arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */
arp.hlen = 6; /* hardware address length */

9
networking/udhcp/arpping.h
View File

@ -11,7 +11,12 @@
#include <netinet/in.h>
struct arpMsg {
struct ethhdr ethhdr; /* Ethernet header */
/* Ethernet header */
u_char h_dest[6]; /* destination ether addr */
u_char h_source[6]; /* source ether addr */
u_short h_proto; /* packet type ID field */
/* ARP packet */
uint16_t htype; /* hardware type (must be ARPHRD_ETHER) */
uint16_t ptype; /* protocol type (must be ETH_P_IP) */
uint8_t hlen; /* hardware address length (must be 6) */
@ -22,7 +27,7 @@ struct arpMsg {
uint8_t tHaddr[6]; /* target's hardware address */
uint8_t tInaddr[4]; /* target's IP address */
uint8_t pad[18]; /* pad for min. Ethernet payload (60 bytes) */
};
} __attribute__ ((packed));
/* function prototypes */
int arpping(uint32_t yiaddr, uint32_t ip, uint8_t *arp, char *interface);