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Remove instances in libssl of the constant 28 (for size of IPv4 header + UDP)

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and instead use the value provided by the underlying BIO. Also provide some
new DTLS_CTRLs so that the library user can set the mtu without needing to
know this constant. These new DTLS_CTRLs provide the capability to set the
link level mtu to be used (i.e. including this IP/UDP overhead). The previous
DTLS_CTRLs required the library user to subtract this overhead first.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 59669b6abf)

Conflicts:
	ssl/d1_both.c
This commit is contained in:
Matt Caswell
2014-12-01 23:58:05 +00:00
parent ccecdb130c
commit 05e769f269
6 changed files with 74 additions and 30 deletions
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54
ssl/d1_both.c
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@@ -156,9 +156,9 @@ static unsigned char bitmask_start_values[] = {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe
static unsigned char bitmask_end_values[] = {0xff, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f};
/* XDTLS: figure out the right values */
static unsigned int g_probable_mtu[] = {1500 - 28, 512 - 28, 256 - 28};
static const unsigned int g_probable_mtu[] = {1500, 512, 256};
static unsigned int dtls1_guess_mtu(unsigned int curr_mtu);
static void dtls1_guess_mtu(SSL *s);
static void dtls1_fix_message_header(SSL *s, unsigned long frag_off,
unsigned long frag_len);
static unsigned char *dtls1_write_message_header(SSL *s,
@@ -226,18 +226,24 @@ void dtls1_hm_fragment_free(hm_fragment *frag)
static void dtls1_query_mtu(SSL *s)
{
if(s->d1->link_mtu)
{
s->d1->mtu = s->d1->link_mtu-BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
s->d1->link_mtu = 0;
}
/* AHA! Figure out the MTU, and stick to the right size */
if (s->d1->mtu < dtls1_min_mtu() && !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU))
if (s->d1->mtu < dtls1_min_mtu(s) && !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU))
{
s->d1->mtu =
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
/* I've seen the kernel return bogus numbers when it doesn't know
* (initial write), so just make sure we have a reasonable number */
if (s->d1->mtu < dtls1_min_mtu())
if (s->d1->mtu < dtls1_min_mtu(s))
{
s->d1->mtu = 0;
s->d1->mtu = dtls1_guess_mtu(s->d1->mtu);
dtls1_guess_mtu(s);
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
s->d1->mtu, NULL);
}
@@ -275,7 +281,7 @@ int dtls1_do_write(SSL *s, int type)
}
#endif
OPENSSL_assert(s->d1->mtu >= dtls1_min_mtu()); /* should have something reasonable now */
OPENSSL_assert(s->d1->mtu >= dtls1_min_mtu(s)); /* should have something reasonable now */
if ( s->init_off == 0 && type == SSL3_RT_HANDSHAKE)
OPENSSL_assert(s->init_num ==
@@ -1299,26 +1305,40 @@ dtls1_write_message_header(SSL *s, unsigned char *p)
return p;
}
unsigned int
dtls1_min_mtu(void)
unsigned int
dtls1_link_min_mtu(void)
{
return (g_probable_mtu[(sizeof(g_probable_mtu) /
sizeof(g_probable_mtu[0])) - 1]);
}
static unsigned int
dtls1_guess_mtu(unsigned int curr_mtu)
unsigned int
dtls1_min_mtu(SSL *s)
{
return dtls1_link_min_mtu()-BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
}
static void
dtls1_guess_mtu(SSL *s)
{
unsigned int curr_mtu;
unsigned int i;
unsigned int mtu_ovr;
curr_mtu = s->d1->mtu;
mtu_ovr = BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
if ( curr_mtu == 0 )
return g_probable_mtu[0] ;
for ( i = 0; i < sizeof(g_probable_mtu)/sizeof(g_probable_mtu[0]); i++)
if ( curr_mtu > g_probable_mtu[i])
return g_probable_mtu[i];
return curr_mtu;
{
curr_mtu = g_probable_mtu[0] - mtu_ovr;
}
else
{
for ( i = 0; i < sizeof(g_probable_mtu)/sizeof(g_probable_mtu[0]); i++)
if ( curr_mtu > g_probable_mtu[i] - mtu_ovr)
return g_probable_mtu[i] - mtu_ovr;
}
s->d1->mtu = curr_mtu;
}
void