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dhcp: Increase buffer size for options in DHCP messages

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According to RFC 2131, the minimum size of the 'options' field is 312
bytes, including the 4 byte magic cookie.  There also does not seem to
be any restriction regarding the message length, previously the length
was rounded to a multiple of 64 bytes.  The latter might have been
because in BOOTP the options field (or rather vendor-specific area as it
was called back then) had a fixed length of 64 bytes (so max(optlen+4, 64)
might actually have been what was intended), but for DHCP the field is
explicitly variable length, so I don't think it's necessary to pad it.
This commit is contained in:
Tobias Brunner
2018-05-18 18:04:01 +02:00
parent 13edecdc20
commit 30e886fe3b
1 changed files with 3 additions and 3 deletions
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src/libcharon/plugins/dhcp/dhcp_socket.c
+3 -3
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@@ -160,7 +160,7 @@ typedef struct __attribute__((packed)) {
} dhcp_option_t; } dhcp_option_t;
/** /**
* DHCP message format, with a maximum size options buffer * DHCP message format, with a minimum size options buffer
*/ */
typedef struct __attribute__((packed)) { typedef struct __attribute__((packed)) {
uint8_t opcode; uint8_t opcode;
@@ -179,7 +179,7 @@ typedef struct __attribute__((packed)) {
char server_hostname[64]; char server_hostname[64];
char boot_filename[128]; char boot_filename[128];
uint32_t magic_cookie; uint32_t magic_cookie;
u_char options[252]; u_char options[308];
} dhcp_t; } dhcp_t;
/** /**
@@ -286,7 +286,7 @@ static bool send_dhcp(private_dhcp_socket_t *this,
{ {
dst = this->dst; dst = this->dst;
} }
len = offsetof(dhcp_t, magic_cookie) + ((optlen + 4) / 64 * 64 + 64); len = offsetof(dhcp_t, magic_cookie) + optlen + 4;
return sendto(this->send, dhcp, len, 0, dst->get_sockaddr(dst), return sendto(this->send, dhcp, len, 0, dst->get_sockaddr(dst),
*dst->get_sockaddr_len(dst)) == len; *dst->get_sockaddr_len(dst)) == len;
} }