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Merge pull request #521 from DrDoof/fix/dhcp-option-length

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dhcp: skip IP and time options that are shorter than four bytes
This commit is contained in:
bloq authored and GitHub committed 2026-09-25 14:20:50 -05:00
2 parents 770926abd1 456a4d9d3f
commit 8ae3f5e70f
1 file changed
+17 -13
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dhcp.c
+17 -13
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@@ -232,19 +232,21 @@ void ip_opt(__xdata uint8_t * ip)
{
dhcp_state.opt_ptr++;
uint8_t len = DHCP_OPT[dhcp_state.opt_ptr++];
*ip++ = DHCP_OPT[dhcp_state.opt_ptr++];
*ip++ = DHCP_OPT[dhcp_state.opt_ptr++];
*ip++ = DHCP_OPT[dhcp_state.opt_ptr++];
*ip++ = DHCP_OPT[dhcp_state.opt_ptr++];
if (len >= 4)
memcpy(ip, &DHCP_OPT[dhcp_state.opt_ptr], 4);
// There may be more than one IP option, such as 2 DNS servers advertised
dhcp_state.opt_ptr += len - 4;
dhcp_state.opt_ptr += len;
}
void long_opt(void)
uint8_t long_opt(void)
{
dhcp_state.opt_ptr++;
dhcp_state.opt_ptr++;
uint8_t len = DHCP_OPT[dhcp_state.opt_ptr++];
if (len < 4) {
dhcp_state.opt_ptr += len;
return 0;
}
long_value = DHCP_OPT[dhcp_state.opt_ptr++];
long_value <<= 8;
long_value |= DHCP_OPT[dhcp_state.opt_ptr++];
@@ -252,6 +254,8 @@ void long_opt(void)
long_value |= DHCP_OPT[dhcp_state.opt_ptr++];
long_value <<= 8;
long_value |= DHCP_OPT[dhcp_state.opt_ptr++];
dhcp_state.opt_ptr += len - 4;
return 1;
}
@@ -275,16 +279,16 @@ void parse_opts(void)
ip_opt(&dhcp_state.broadcast[0]);
break;
case DHCP_LEASE:
long_opt();
dhcp_state.lease = long_value;
if (long_opt())
dhcp_state.lease = long_value;
break;
case DHCP_REBIND:
long_opt();
dhcp_state.rebind = long_value;
if (long_opt())
dhcp_state.rebind = long_value;
break;
case DHCP_RENEWAL:
long_opt();
dhcp_state.renewal = long_value;
if (long_opt())
dhcp_state.renewal = long_value;
break;
case DHCP_END:
break;