These are all changes coming from pending muvm experiments where I'm
trying to speed up and simplify the networking setup in the guest.
v5: In 2/3, keep the condition:
(opts[53].clen <= 0 || opts[53].c[0] == DHCPREQUEST)
as it was, instead of replacing || with &&
v4: In 1/3, don't swap the "BOOTP" and "DHCP" labels: we want to
print
"BOOTP" if option 53 isn't there or has zero length, not the other
way around. Further, check that clen for option 53 is > 0 before
checking if it's a DHCPDISCOVER. Given that DHCPDISCOVER is 1 (not
0), this happened to already work for BOOTP, but it worked by
mistake
v3: In 1/3, set 'slen' for options we won't send to -1 in dhcp_init(),
and reset it for option 80 every time we handle a DHCP request. Add
a comment about DHCP needing a valid message type (option 53)
v2: In 3/3, add in4addr_broadcast to ip.h, instead of open-coding it in
dhcp()
Stefano Brivio (3):
dhcp: Use -1 as "missing option" length instead of 0
dhcp: Introduce support for Rapid Commit (option 80, RFC 4039)
dhcp: Honour broadcast flag (RFC 2131, 4.1)
dhcp.c | 53 +++++++++++++++++++++++++++++++++++++++++------------
ip.h | 3 +++
2 files changed, 44 insertions(+), 12 deletions(-)
--
2.43.0
We want to add support for option 80 (Rapid Commit, RFC 4039), whose
length is 0.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>
---
dhcp.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/dhcp.c b/dhcp.c
index a06f143..387aee3 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -36,9 +36,9 @@
/**
* struct opt - DHCP option
* @sent: Convenience flag, set while filling replies
- * @slen: Length of option defined for server
+ * @slen: Length of option defined for server, -1 if not going to be sent
* @s: Option payload from server
- * @clen: Length of option received from client
+ * @clen: Length of option received from client, -1 if not received
* @c: Option payload from client
*/
struct opt {
@@ -68,6 +68,11 @@ static struct opt opts[255];
*/
void dhcp_init(void)
{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(opts); i++)
+ opts[i].slen = -1;
+
opts[1] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Mask */
opts[3] = (struct opt) { 0, 4, { 0 }, 0, { 0 }, }; /* Router */
opts[51] = (struct opt) { 0, 4, { 0xff,
@@ -154,17 +159,17 @@ static int fill(struct msg *m)
* option 53 at the beginning of the list.
* Put it there explicitly, unless requested via option 55.
*/
- if (!memchr(opts[55].c, 53, opts[55].clen))
+ if (opts[55].clen > 0 && !memchr(opts[55].c, 53, opts[55].clen))
fill_one(m, 53, &offset);
for (i = 0; i < opts[55].clen; i++) {
o = opts[55].c[i];
- if (opts[o].slen)
+ if (opts[o].slen != -1)
fill_one(m, o, &offset);
}
for (o = 0; o < 255; o++) {
- if (opts[o].slen && !opts[o].sent)
+ if (opts[o].slen != -1 && !opts[o].sent)
fill_one(m, o, &offset);
}
@@ -264,6 +269,9 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
".\xc0");
}
}
+
+ if (!opts[119].slen)
+ opts[119].slen = -1;
}
/**
@@ -313,6 +321,9 @@ int dhcp(const struct ctx *c, const struct pool *p)
offset += offsetof(struct msg, o);
+ for (i = 0; i < ARRAY_SIZE(opts); i++)
+ opts[i].clen = -1;
+
while (opt_off + 2 < opt_len) {
const uint8_t *olen, *val;
uint8_t *type;
@@ -331,11 +342,12 @@ int dhcp(const struct ctx *c, const struct pool *p)
opt_off += *olen + 2;
}
- if (opts[53].c[0] == DHCPDISCOVER) {
+ if (opts[53].clen > 0 && opts[53].c[0] == DHCPDISCOVER) {
info("DHCP: offer to discover");
opts[53].s[0] = DHCPOFFER;
- } else if (opts[53].c[0] == DHCPREQUEST || !opts[53].clen) {
- info("%s: ack to request", opts[53].clen ? "DHCP" :
"BOOTP");
+ } else if (opts[53].clen <= 0 || opts[53].c[0] == DHCPREQUEST) {
+ info("%s: ack to request", /* DHCP needs a valid message type */
+ (opts[53].clen <= 0) ? "BOOTP" : "DHCP");
opts[53].s[0] = DHCPACK;
} else {
return -1;
@@ -374,6 +386,8 @@ int dhcp(const struct ctx *c, const struct pool *p)
((struct in_addr *)opts[6].s)[i] = c->ip4.dns[i];
opts[6].slen += sizeof(uint32_t);
}
+ if (!opts[6].slen)
+ opts[6].slen = -1;
if (!c->no_dhcp_dns_search)
opt_set_dns_search(c, sizeof(m->o));
--
2.43.0
I'm trying to speed up and simplify IP address acquisition in muvm.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>
---
dhcp.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/dhcp.c b/dhcp.c
index 387aee3..a16cde8 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -342,9 +342,16 @@ int dhcp(const struct ctx *c, const struct pool *p)
opt_off += *olen + 2;
}
+ opts[80].slen = -1;
if (opts[53].clen > 0 && opts[53].c[0] == DHCPDISCOVER) {
- info("DHCP: offer to discover");
- opts[53].s[0] = DHCPOFFER;
+ if (opts[80].clen == -1) {
+ info("DHCP: offer to discover");
+ opts[53].s[0] = DHCPOFFER;
+ } else {
+ info("DHCP: ack to discover (Rapid Commit)");
+ opts[53].s[0] = DHCPACK;
+ opts[80].slen = 0;
+ }
} else if (opts[53].clen <= 0 || opts[53].c[0] == DHCPREQUEST) {
info("%s: ack to request", /* DHCP needs a valid message type */
(opts[53].clen <= 0) ? "BOOTP" : "DHCP");
--
2.43.0
It's widely considered a legacy option nowadays, and I've haven't seen
clients setting it since Windows 95, but it's convenient for a minimal
DHCP client not using raw IP sockets such as what I'm playing with for
muvm.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
Reviewed-by: David Gibson <david(a)gibson.dropbear.id.au>
---
dhcp.c | 12 ++++++++++--
ip.h | 3 +++
2 files changed, 13 insertions(+), 2 deletions(-)
diff --git a/dhcp.c b/dhcp.c
index a16cde8..d8515aa 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -112,6 +112,8 @@ struct msg {
uint32_t xid;
uint16_t secs;
uint16_t flags;
+#define FLAG_BROADCAST htons_constant(0x8000)
+
uint32_t ciaddr;
struct in_addr yiaddr;
uint32_t siaddr;
@@ -285,10 +287,10 @@ int dhcp(const struct ctx *c, const struct pool *p)
{
size_t mlen, dlen, offset = 0, opt_len, opt_off = 0;
char macstr[ETH_ADDRSTRLEN];
+ struct in_addr mask, dst;
const struct ethhdr *eh;
const struct iphdr *iph;
const struct udphdr *uh;
- struct in_addr mask;
unsigned int i;
struct msg *m;
@@ -400,7 +402,13 @@ int dhcp(const struct ctx *c, const struct pool *p)
opt_set_dns_search(c, sizeof(m->o));
dlen = offsetof(struct msg, o) + fill(m);
- tap_udp4_send(c, c->ip4.our_tap_addr, 67, c->ip4.addr, 68, m, dlen);
+
+ if (m->flags & FLAG_BROADCAST)
+ dst = in4addr_broadcast;
+ else
+ dst = c->ip4.addr;
+
+ tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, m, dlen);
return 1;
}
diff --git a/ip.h b/ip.h
index 0742612..1544dbf 100644
--- a/ip.h
+++ b/ip.h
@@ -101,4 +101,7 @@ static const struct in6_addr in6addr_ll_all_nodes = {
},
};
+/* IPv4 Limited Broadcast (RFC 919, Section 7), 255.255.255.255 */
+static const struct in_addr in4addr_broadcast = { 0xffffffff };
+
#endif /* IP_H */
--
2.43.0