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make sure response size assert applies in the empty response case; cleanup; add more comments

This commit is contained in:
rakslice 2020-11-19 18:29:06 -08:00
parent ff0a825356
commit faeb5fa2e1
1 changed files with 33 additions and 12 deletions
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45
BasiliskII/src/slirp/socket.c
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@ -621,8 +621,11 @@ struct R_DATA
unsigned short data_len;
};
#pragma pack(pop)
#define POP_STRUCT(vartype, varname, data, len) \
/** Create local variable varname of type vartype,
* fill it from the buffer data, observing its length len,
* and adjust data and len to reflect the remaining data */
#define POP_DATA(vartype, varname, data, len) \
assert(len >= sizeof(vartype)); \
vartype varname; \
memcpy(&varname, data, sizeof(vartype)); \
@ -630,9 +633,29 @@ struct R_DATA
len -= sizeof(vartype)
/** Create local const char * varname pointing
* to the C string in the buffer data, observing its length len,
* and adjust data and len to reflect the remaining data */
#define POP_STR(varname, data, len) \
const char * varname; \
{ \
int pop_str_len = strnlen(data, len); \
if (pop_str_len == len) { \
varname = NULL; \
} else { \
varname = data; \
} \
data += pop_str_len + 1; \
len -= pop_str_len + 1; \
}
static void inject_udp_packet_to_guest(struct socket * so, struct sockaddr_in addr, caddr_t packet_data, int packet_len) {
struct mbuf *m;
int len;
/** This is like sorecvfrom(), but just adds a packet with the
* supplied data instead of reading the packet to add from the socket */
if (!(m = m_get())) return;
m->m_data += if_maxlinkhdr;
@ -654,7 +677,7 @@ static void inject_udp_packet_to_guest(struct socket * so, struct sockaddr_in ad
/* Decode hostname from the format used in DNS
e.g. "\009something\004else\003com" for "something.else.com." */
static char * decode_dns_name(char * data) {
static char * decode_dns_name(const char * data) {
int query_str_len = strlen(data);
char * decoded_name_str = malloc(query_str_len + 1);
@ -699,7 +722,7 @@ static bool resolve_dns_request(struct socket * so, struct sockaddr_in addr, cad
const caddr_t packet = data;
const int packet_len = len;
POP_STRUCT(struct DNS_HEADER, h, data, len);
POP_DATA(struct DNS_HEADER, h, data, len);
if (h.qr != 0) {
D("DNS packet is not a request\n");
@ -726,9 +749,9 @@ static bool resolve_dns_request(struct socket * so, struct sockaddr_in addr, cad
return false;
}
char * original_query_str = data;
int query_str_len = strnlen(data, len);
if (query_str_len == len) { // went off end of packet
POP_STR(original_query_str, data, len);
if (original_query_str == NULL) {
// went off end of packet
D("Unterminated DNS query string\n");
return false;
}
@ -741,10 +764,7 @@ static bool resolve_dns_request(struct socket * so, struct sockaddr_in addr, cad
D("DNS host query for %s\n", decoded_name_str);
data += query_str_len + 1;
len -= query_str_len + 1;
POP_STRUCT(struct QUESTION, qinfo, data, len);
POP_DATA(struct QUESTION, qinfo, data, len);
if (ntohs(qinfo.qtype) != 1 /* type A */ || ntohs(qinfo.qclass) != 1 /* class IN */ ) {
D("DNS host query for %s: Request isn't the supported type (INET A query)\n", decoded_name_str);
@ -837,9 +857,10 @@ static bool resolve_dns_request(struct socket * so, struct sockaddr_in addr, cad
memcpy(response_packet + response_pos, cur_addr, sizeof(struct in_addr));
response_pos += sizeof(struct in_addr);
}
assert(response_pos == response_size);
}
assert(response_pos == response_size);
D("DNS host query for %s: Injecting DNS response directly to guest\n", decoded_name_str);
inject_udp_packet_to_guest(so, addr, response_packet, response_size);