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ipfw: make it possible to specify MTU for "unreach needfrag" action

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Reviewed by:		ae, pauamma
Differential revision:	https://reviews.freebsd.org/D36140
This commit is contained in:
Gleb Smirnoff 2022-08-17 08:24:11 -07:00
parent e7abb89701
commit 05b9737f10
4 changed files with 41 additions and 6 deletions
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10
sbin/ipfw/ipfw.8
View File

@ -1,7 +1,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd June 4, 2022
.Dd August 17, 2022
.Dt IPFW 8
.Os
.Sh NAME
@ -1080,7 +1080,7 @@ Send a copy of packets matching this rule to the
socket bound to port
.Ar port .
The search continues with the next rule.
.It Cm unreach Ar code
.It Cm unreach Ar code Op mtu
Discard packets that match this rule, and try to send an ICMP
unreachable notice with code
.Ar code ,
@ -1093,6 +1093,12 @@ is a number from 0 to 255, or one of these aliases:
.Cm toshost , filter-prohib , host-precedence
or
.Cm precedence-cutoff .
The
.Cm needfrag
code may have an optional
.Ar mtu
parameter.
If specified, the MTU value will be put into generated ICMP packet.
The search terminates.
.It Cm unreach6 Ar code
Discard packets that match this rule, and try to send an ICMPv6

15
sbin/ipfw/ipfw2.c
View File

@ -1890,6 +1890,10 @@ print_action_instruction(struct buf_pr *bp, const struct format_opts *fo,
bprintf(bp, "abort");
else if (cmd->arg1 == ICMP_UNREACH_HOST)
bprintf(bp, "reject");
else if (cmd->arg1 == ICMP_UNREACH_NEEDFRAG &&
cmd->len == F_INSN_SIZE(ipfw_insn_u16))
bprintf(bp, "needfrag %u",
((const ipfw_insn_u16 *)cmd)->ports[0]);
else
print_reject_code(bp, cmd->arg1);
break;
@ -3992,6 +3996,17 @@ compile_rule(char *av[], uint32_t *rbuf, int *rbufsize, struct tidx *tstate)
NEED1("missing reject code");
fill_reject_code(&action->arg1, *av);
av++;
if (action->arg1 == ICMP_UNREACH_NEEDFRAG && isdigit(**av)) {
uint16_t mtu;
mtu = strtoul(*av, NULL, 10);
if (mtu < 68 || mtu >= IP_MAXPACKET)
errx(EX_DATAERR, "illegal argument for %s",
*(av - 1));
action->len = F_INSN_SIZE(ipfw_insn_u16);
((ipfw_insn_u16 *)action)->ports[0] = mtu;
av++;
}
break;
case TOK_UNREACH6:

15
sys/netpfil/ipfw/ip_fw2.c
View File

@ -993,8 +993,17 @@ send_reject6(struct ip_fw_args *args, int code, u_int hlen, struct ip6_hdr *ip6)
* sends a reject message, consuming the mbuf passed as an argument.
*/
static void
send_reject(struct ip_fw_args *args, int code, int iplen, struct ip *ip)
send_reject(struct ip_fw_args *args, const ipfw_insn *cmd, int iplen,
struct ip *ip)
{
int code, mtu;
code = cmd->arg1;
if (code == ICMP_UNREACH_NEEDFRAG &&
cmd->len == F_INSN_SIZE(ipfw_insn_u16))
mtu = ((const ipfw_insn_u16 *)cmd)->ports[0];
else
mtu = 0;
#if 0
/* XXX When ip is not guaranteed to be at mtod() we will
@ -1008,7 +1017,7 @@ send_reject(struct ip_fw_args *args, int code, int iplen, struct ip *ip)
#endif
if (code != ICMP_REJECT_RST && code != ICMP_REJECT_ABORT) {
/* Send an ICMP unreach */
icmp_error(args->m, ICMP_UNREACH, code, 0L, 0);
icmp_error(args->m, ICMP_UNREACH, code, 0L, mtu);
} else if (code == ICMP_REJECT_RST && args->f_id.proto == IPPROTO_TCP) {
struct tcphdr *const tcp =
L3HDR(struct tcphdr, mtod(args->m, struct ip *));
@ -3042,7 +3051,7 @@ do { \
is_icmp_query(ICMP(ulp))) &&
!(m->m_flags & (M_BCAST|M_MCAST)) &&
!IN_MULTICAST(ntohl(dst_ip.s_addr))) {
send_reject(args, cmd->arg1, iplen, ip);
send_reject(args, cmd, iplen, ip);
m = args->m;
}
/* FALLTHROUGH */

7
sys/netpfil/ipfw/ip_fw_sockopt.c
View File

@ -2000,12 +2000,17 @@ check_ipfw_rule_body(ipfw_insn *cmd, int cmd_len, struct rule_check_info *ci)
goto check_action;
case O_CHECK_STATE:
ci->object_opcodes++;
goto check_size;
case O_REJECT:
/* "unreach needfrag" has variable len. */
if ((cmdlen == F_INSN_SIZE(ipfw_insn) ||
cmdlen == F_INSN_SIZE(ipfw_insn_u16)))
goto check_action;
/* FALLTHROUGH */
case O_FORWARD_MAC: /* XXX not implemented yet */
case O_COUNT:
case O_ACCEPT:
case O_DENY:
case O_REJECT:
case O_SETDSCP:
#ifdef INET6
case O_UNREACH6: