From: Stefano Brivio <sbrivio@redhat.com>
To: passt-dev@passt.top
Cc: David Gibson <david@gibson.dropbear.id.au>,
Yalan Zhang <yalzhang@redhat.com>
Subject: [PATCH] dhcp: Fix netmask calculation for option 1 from prefix length
Date: Thu, 16 Feb 2023 02:07:52 +0100 [thread overview]
Message-ID: <20230216010752.2224192-1-sbrivio@redhat.com> (raw)
Similar to the conf_print() fix from commit 4129764ecaeb ("conf: Fix
mask calculation from prefix_len in conf_print()"): to calculate an
IPv4 netmask from the prefix length, we need to left shift 32 all-one
bits by 32 minus the prefix length -- not by the prefix length
itself.
Reported-by: Yalan Zhang <yalzhang@redhat.com>
Fixes: dd09cceaee21 ("Minor improvements to IPv4 netmask handling")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
dhcp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/dhcp.c b/dhcp.c
index 6088886..edab780 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -335,7 +335,7 @@ int dhcp(const struct ctx *c, const struct pool *p)
m->chaddr[3], m->chaddr[4], m->chaddr[5]);
m->yiaddr = c->ip4.addr;
- mask.s_addr = htonl(0xffffffff << c->ip4.prefix_len);
+ mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len));
memcpy(opts[1].s, &mask, sizeof(mask));
memcpy(opts[3].s, &c->ip4.gw, sizeof(c->ip4.gw));
memcpy(opts[54].s, &c->ip4.gw, sizeof(c->ip4.gw));
--
@@ -335,7 +335,7 @@ int dhcp(const struct ctx *c, const struct pool *p)
m->chaddr[3], m->chaddr[4], m->chaddr[5]);
m->yiaddr = c->ip4.addr;
- mask.s_addr = htonl(0xffffffff << c->ip4.prefix_len);
+ mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len));
memcpy(opts[1].s, &mask, sizeof(mask));
memcpy(opts[3].s, &c->ip4.gw, sizeof(c->ip4.gw));
memcpy(opts[54].s, &c->ip4.gw, sizeof(c->ip4.gw));
--
2.35.1
next reply other threads:[~2023-02-16 1:07 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-16 1:07 Stefano Brivio [this message]
2023-02-16 3:48 ` [PATCH] dhcp: Fix netmask calculation for option 1 from prefix length David Gibson
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