From: Matt Jaffa <email@hidden>
To: Justin Walker <email@hidden>
CC: darwin-kernel Dev <email@hidden>
Subject: Re: dlil_inject_if_input
Date: Sat, 18 Sep 2004 21:26:40 -0600
this helps a lot,
I am using MGET now, and not using MALLOC for the mbuf to save myself the
trouble of later problems.
Now when I print out the hex values of the whole mbuf, they are all
printing out correct.
But now when I inject this mbuf into the input, the system crashes. But if
I comment out the
dlil_inject_if_input, it doesn't crash.
Is my mbuf set up wrong??
char * httpresponse = (char*)_MALLOC(180,M_FREE,M_NOWAIT);
sprintf(httpresponse,"HTTP/1.1 200 OK\r\nCache-Control: no-store,
no-cache\r\nContent-Type: text/html\r\n\r\n <HTML><BODY>This is the block
page</BODY></HTML>");
struct mbuf * testin;
MGET(testin,M_NOWAIT,M_MBUF);
struct ip newip;// = (struct ip*)_MALLOC(sizeof(struct
ip),M_FREE,M_NOWAIT);
u_char vhl = 0x45;
memcpy(&newip, &vhl,1);
newip.ip_hl = 5;
printf("ipHeader version: %d\n", ipHeader->ip_v);
printf("ipHeader hdrleng: %d\n", ipHeader->ip_hl);
printf("newipheader: %d\n", newip.ip_v);
printf("newipheader: %d\n", newip.ip_hl);
newip.ip_v = 4;//ipHeader->ip_v;
newip.ip_tos = 0;//ipHeader->ip_tos;
int data_len = strlen(httpresponse);
newip.ip_len = sizeof(struct ip) + sizeof(struct tcphdr) + data_len;
newip.ip_id = 34234;
newip.ip_off = 0x0000;
newip.ip_ttl = 35;
newip.ip_p = ipHeader->ip_p;
newip.ip_sum = 0;
memcpy(&(newip.ip_src), &(ipHeader->ip_dst), sizeof(struct in_addr));
memcpy(&(newip.ip_dst), &(ipHeader->ip_src), sizeof(struct in_addr));
struct tcphdr newtcp;// = (struct tcphdr*)_MALLOC(sizeof(struct
tcphdr),M_FREE,M_NOWAIT);
newtcp.th_sport = tester->th_dport;
newtcp.th_dport = tester->th_sport;
newtcp.th_ack = tester->th_seq;
newtcp.th_seq = htons(tester->th_seq +1);
newtcp.th_flags = (TH_ACK|TH_FIN|TH_PUSH);
newtcp.th_off = sizeof(struct tcphdr);
newtcp.th_x2 = 0;
newtcp.th_win = 65535;
newtcp.th_sum = 0;
newtcp.th_urp = 0;
testin->m_data += 20;
memcpy(testin->m_data,&newip,sizeof(struct ip));
testin->m_len = sizeof(struct ip);
testin->m_pkthdr.len = sizeof(struct ip);
testin->m_data += sizeof(struct ip);
memcpy(testin->m_data,&newtcp,sizeof(struct tcphdr));
testin->m_data += sizeof(struct tcphdr);
memcpy(testin->m_data,httpresponse,data_len);
testin->m_len = (sizeof(struct ip) + sizeof(struct tcphdr) + data_len);
testin->m_pkthdr.len = (sizeof(struct ip) + sizeof(struct tcphdr) +
data_len);
testin->m_data -= (sizeof(struct ip) + sizeof(struct tcphdr));
unsigned char * test = mtod(testin, unsigned char*);
int i = 0;
while(i < testin->m_pkthdr.len) {
printf("%x ",test[i]);
i++;
}
printf("\n");
int testing = dlil_inject_if_input(testin,frame_type,ipv4ID);
printf("Here is the result: %d\n", testing);
So I have a IP header 20 bytes, and a TCP header 20 bytes, no options, and
data for the TCP, not shown is the checksum calculating, but that is not
crashing, it is the dlil_inject_if_input, it doesn't like my mbuf.
Anyone notice anything bad? Sequence and Ack I know is wrong but don't
know how to fix it.
Any help on the mbuf injecting and the Seq and Ack would be great thanks.
Matt
On Sep 17, 2004, at 11:39 PM, Justin Walker wrote:
On Sep 17, 2004, at 21:55, Matt Jaffa wrote:
Here is how I am formulating my IP header:
ipHeader is the ip header pulled out from the mbuf that I am not letting
out into the internet.
struct ip* newip = (struct ip*)_MALLOC(sizeof(struct
ip),M_FREE,M_NOWAIT);
Why are you using _MALLOC instead of (say) MGET? You may be asking for
trouble here, unless you are taking care of properly releasing this
storage.
newip->ip_hl = 5;
newip->ip_v = ipHeader->ip_v;
printf("ipHeader version: %d\n", ipHeader->ip_v);
printf("ipHeader hdrleng: %d\n", ipHeader->ip_hl);
printf("newipheader: %d\n", newip->ip_v);
printf("newipheader: %d\n", newip->ip_hl);
Well, what do the printf's say? FWIW, the kernel code defines _IP_VHL,
and refers to the two fields as the combined field 'ip_vhl'. Why not
print a hex dump of the first few bytes of the two IP headers? That may
provide a clue (and it avoids any funky behavior based on bit-field
operations).
newip->ip_tos = 0;
int data_len = strlen(httpresponse); // this is the
HTTP/1.1 response length of the tcp data I will inject into the input
I assume the length of this canned response is small enough that you
don't have to worry about overflowing whatever you are using for buffers.
newip->ip_len = sizeof(struct ip) + sizeof(struct tcphdr) + data_len;
newip->ip_id = 34234;
newip->ip_off = 0x4000;
BTW, I would set ip_off to zero.
newip->ip_ttl = 35;
newip->ip_p = ipHeader->ip_p;
newip->ip_sum = 0;
You compute the checksum later, right?
memcpy(&(newip->ip_src), &(ipHeader->ip_dst), sizeof(struct
in_addr));
memcpy(&(newip->ip_dst), &(ipHeader->ip_src), sizeof(struct
in_addr));
For correctness, you might want to assure that the values you are copying
are in network order (since the IP stack has set it up that way on
output). For PowerPC, host order and network order are the same, but it
pays to keep this straight in your code.
despite the fact that some of the other stuff might be wrong, why
wouldn't the ip_v be the right version? The output does print out 4 like
it should be.
Any number of things could be wrong. One obvious possibility is that
when you finally cons up the frame you inject, you aren't matching the
assumptions of the input processing, so that when that code looks looks
at the IP header, it's not seeing your IP header (e.g., there should be
an ethernet header, but isn't; or there is an ethernet header, but there
should not be one).
To emphasize a point above, do *not* allocate mbufs other than by MGET
(or similar call) unless you are actually obeying all the rules for
supplying your own buffers (and freeing same).
Regards,
Justin
--
Justin C. Walker, Curmudgeon-At-Large *
Institute for General Semantics | "Weaseling out of things is what
| separates us from the animals.
| Well, except the weasel."
| - Homer J Simpson
*-------------------------------------- *-------------------------------*
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