Jacob B Schwartz: more click

[Eddie Kohler]

this guy is sending me mucho mail.

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To: eddietwo at MIT.EDU
Subject: more click
Date: Wed, 17 May 2000 15:04:11 -0400
From: Jacob B Schwartz <quark at MIT.EDU>


If you don't mind me bugging you again:
Do the "unused" parts of the structs indicate zero bits that should
be in the ICMP data in the IP packet?  That is, in the generic case,
the packet header and 8 bits should come some number of bits after
the checksum?  Or what?


/* most icmp request types */
struct icmp_generic 
{
  unsigned char icmp_type;              /* one of the ICMP_TYPE_*'s above */
  unsigned char icmp_code;              /* one of the ICMP_CODE_*'s above */
  unsigned short icmp_cksum;            /* 16 1's comp csum */
  unsigned int unused;                  /* should be zero */
  /* followed by original IP header and first 8 octets of data */
};


/* parameter problem header */
struct icmp_param 
{
  unsigned char icmp_type;              /* one of the ICMP_TYPE_*'s above */
  unsigned char icmp_code;              /* one of the ICMP_CODE_*'s above */
  unsigned short icmp_cksum;            /* 16 1's comp csum */
  unsigned char pointer;                /* which octect was a problem */
  unsigned char unused[3];              /* should be zero */
  /* followed by original IP header and first 8 octets of data */
};

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