From: Enrique Llorente <ellorent@redhat.com>
To: passt-dev@passt.top
Cc: Enrique Llorente <ellorent@redhat.com>
Subject: [PATCH v2] dhcp: Don't re-use request message for reply
Date: Tue, 4 Feb 2025 10:43:37 +0100 [thread overview]
Message-ID: <20250204094337.249568-1-ellorent@redhat.com> (raw)
The logic composing the DHCP reply message is reusing the request
message to compose it, future long options like FQDN may
exceed the request message limit making it go beyond the lower
bound.
This change creates a new reply message with a fixed options size of 308
and fills it in with proper fields from requests adding on top the generated
options, this way the reply lower bound does not depend on the request.
Signed-off-by: Enrique Llorente <ellorent@redhat.com>
---
dhcp.c | 27 ++++++++++++++++++++-------
1 file changed, 20 insertions(+), 7 deletions(-)
diff --git a/dhcp.c b/dhcp.c
index d8515aa..2a23ed4 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -151,9 +151,6 @@ static int fill(struct msg *m)
{
int i, o, offset = 0;
- m->op = BOOTREPLY;
- m->secs = 0;
-
for (o = 0; o < 255; o++)
opts[o].sent = 0;
@@ -291,8 +288,9 @@ int dhcp(const struct ctx *c, const struct pool *p)
const struct ethhdr *eh;
const struct iphdr *iph;
const struct udphdr *uh;
+ struct msg const *m;
+ struct msg reply;
unsigned int i;
- struct msg *m;
eh = packet_get(p, 0, offset, sizeof(*eh), NULL);
offset += sizeof(*eh);
@@ -321,6 +319,22 @@ int dhcp(const struct ctx *c, const struct pool *p)
m->op != BOOTREQUEST)
return -1;
+ reply.op = BOOTREPLY;
+ reply.htype = m->htype;
+ reply.hlen = m->hlen;
+ reply.hops = 0;
+ reply.xid = m->xid;
+ reply.secs = 0;
+ reply.flags = m->flags;
+ reply.ciaddr = m->ciaddr;
+ reply.yiaddr = c->ip4.addr;
+ reply.siaddr = 0;
+ reply.giaddr = m->giaddr;
+ memcpy(&reply.chaddr, m->chaddr, sizeof(reply.chaddr));
+ memset(&reply.sname, 0, sizeof(reply.sname));
+ memset(&reply.file, 0, sizeof(reply.file));
+ reply.magic = m->magic;
+
offset += offsetof(struct msg, o);
for (i = 0; i < ARRAY_SIZE(opts); i++)
@@ -364,7 +378,6 @@ int dhcp(const struct ctx *c, const struct pool *p)
info(" from %s", eth_ntop(m->chaddr, macstr, sizeof(macstr)));
- m->yiaddr = c->ip4.addr;
mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len));
memcpy(opts[1].s, &mask, sizeof(mask));
memcpy(opts[3].s, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw));
@@ -401,14 +414,14 @@ int dhcp(const struct ctx *c, const struct pool *p)
if (!c->no_dhcp_dns_search)
opt_set_dns_search(c, sizeof(m->o));
- dlen = offsetof(struct msg, o) + fill(m);
+ dlen = offsetof(struct msg, o) + fill(&reply);
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);
+ tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, &reply, dlen);
return 1;
}
--
@@ -151,9 +151,6 @@ static int fill(struct msg *m)
{
int i, o, offset = 0;
- m->op = BOOTREPLY;
- m->secs = 0;
-
for (o = 0; o < 255; o++)
opts[o].sent = 0;
@@ -291,8 +288,9 @@ int dhcp(const struct ctx *c, const struct pool *p)
const struct ethhdr *eh;
const struct iphdr *iph;
const struct udphdr *uh;
+ struct msg const *m;
+ struct msg reply;
unsigned int i;
- struct msg *m;
eh = packet_get(p, 0, offset, sizeof(*eh), NULL);
offset += sizeof(*eh);
@@ -321,6 +319,22 @@ int dhcp(const struct ctx *c, const struct pool *p)
m->op != BOOTREQUEST)
return -1;
+ reply.op = BOOTREPLY;
+ reply.htype = m->htype;
+ reply.hlen = m->hlen;
+ reply.hops = 0;
+ reply.xid = m->xid;
+ reply.secs = 0;
+ reply.flags = m->flags;
+ reply.ciaddr = m->ciaddr;
+ reply.yiaddr = c->ip4.addr;
+ reply.siaddr = 0;
+ reply.giaddr = m->giaddr;
+ memcpy(&reply.chaddr, m->chaddr, sizeof(reply.chaddr));
+ memset(&reply.sname, 0, sizeof(reply.sname));
+ memset(&reply.file, 0, sizeof(reply.file));
+ reply.magic = m->magic;
+
offset += offsetof(struct msg, o);
for (i = 0; i < ARRAY_SIZE(opts); i++)
@@ -364,7 +378,6 @@ int dhcp(const struct ctx *c, const struct pool *p)
info(" from %s", eth_ntop(m->chaddr, macstr, sizeof(macstr)));
- m->yiaddr = c->ip4.addr;
mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len));
memcpy(opts[1].s, &mask, sizeof(mask));
memcpy(opts[3].s, &c->ip4.guest_gw, sizeof(c->ip4.guest_gw));
@@ -401,14 +414,14 @@ int dhcp(const struct ctx *c, const struct pool *p)
if (!c->no_dhcp_dns_search)
opt_set_dns_search(c, sizeof(m->o));
- dlen = offsetof(struct msg, o) + fill(m);
+ dlen = offsetof(struct msg, o) + fill(&reply);
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);
+ tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, &reply, dlen);
return 1;
}
--
2.47.0
next reply other threads:[~2025-02-04 9:43 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-04 9:43 Enrique Llorente [this message]
2025-02-07 10:26 ` [PATCH v2] dhcp: Don't re-use request message for reply Stefano Brivio
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250204094337.249568-1-ellorent@redhat.com \
--to=ellorent@redhat.com \
--cc=passt-dev@passt.top \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://passt.top/passt
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for IMAP folder(s).