Re: [PATCH v2 21/23] conf, fwd: Stricter rule checking in fwd_rule_add()

On Fri, 10 Apr 2026 11:03:07 +1000 David Gibson wrote:

Although fwd_rule_add() performs some sanity checks on the rule it is given, there are invalid rules we don't check for, assuming that its callers will do that.

That won't be enough when we can get rules inserted by a dynamic update client without going through the existing parsing code. So, add stricter checks to fwd_rule_add(), which is now possible thanks to the capabilities bits in the struct fwd_table. Where those duplicate existing checks in the callers, remove the old copies.

Signed-off-by: David Gibson --- conf.c | 19 ------------------- fwd.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 46 insertions(+), 24 deletions(-)

diff --git a/conf.c b/conf.c index b7a4459e..31627209 100644 --- a/conf.c +++ b/conf.c @@ -310,10 +310,6 @@ static void conf_ports_spec(struct fwd_table *fwd, uint8_t proto, if (p != ep) /* Garbage after the ranges */ goto bad;

- if (orig_range.first == 0) { - die("Can't forward port 0 included in '%s'", spec); - } - conf_ports_range_except(fwd, proto, addr, ifname, orig_range.first, orig_range.last, exclude, @@ -356,11 +352,6 @@ static void conf_ports(char optname, const char *optarg, struct fwd_table *fwd) return; }

- if (proto == IPPROTO_TCP && !(fwd->caps & FWD_CAP_TCP)) - die("TCP port forwarding requested but TCP is disabled"); - if (proto == IPPROTO_UDP && !(fwd->caps & FWD_CAP_UDP)) - die("UDP port forwarding requested but UDP is disabled"); - strncpy(buf, optarg, sizeof(buf) - 1);

if ((spec = strchr(buf, '/'))) { @@ -405,16 +396,6 @@ static void conf_ports(char optname, const char *optarg, struct fwd_table *fwd) addr = NULL; }

- if (addr) { - if (!(fwd->caps & FWD_CAP_IPV4) && inany_v4(addr)) { - die("IPv4 is disabled, can't use -%c %s", - optname, optarg); - } else if (!(fwd->caps & FWD_CAP_IPV6) && !inany_v4(addr)) { - die("IPv6 is disabled, can't use -%c %s", - optname, optarg); - } - } - if (optname == 'T' || optname == 'U') { assert(!addr && !ifname);

diff --git a/fwd.c b/fwd.c index c7fd1a9d..98b04d0c 100644 --- a/fwd.c +++ b/fwd.c @@ -367,17 +367,58 @@ int fwd_rule_add(struct fwd_table *fwd, const struct fwd_rule *new) new->first, new->last); return -EINVAL; } + if (!new->first) { + warn("Forwarding rule atttempts to map from port 0"); + return -EINVAL; + } + if (!new->to || (new->to + new->last - new->first) < new->to) { + warn("Forwarding rule atttempts to map to port 0");

Nit: attempts

+ return -EINVAL; + } if (new->flags & ~allowed_flags) { warn("Rule has invalid flags 0x%hhx", new->flags & ~allowed_flags); return -EINVAL; } - if (new->flags & FWD_DUAL_STACK_ANY && - !inany_equals(&new->addr, &inany_any6)) { - char astr[INANY_ADDRSTRLEN]; + if (new->flags & FWD_DUAL_STACK_ANY) { + if (!inany_equals(&new->addr, &inany_any6)) { + char astr[INANY_ADDRSTRLEN];

- warn("Dual stack rule has non-wildcard address %s", - inany_ntop(&new->addr, astr, sizeof(astr))); + warn("Dual stack rule has non-wildcard address %s", + inany_ntop(&new->addr, astr, sizeof(astr))); + return -EINVAL; + } + if (!(fwd->caps & FWD_CAP_IPV4)) { + warn("Dual stack forward, but IPv4 not enabled"); + return -EINVAL; + } + if (!(fwd->caps & FWD_CAP_IPV6)) { + warn("Dual stack forward, but IPv6 not enabled"); + return -EINVAL; + } + } else { + if (inany_v4(&new->addr) && !(fwd->caps & FWD_CAP_IPV4)) { + warn("IPv4 forward, but IPv4 not enabled"); + return -EINVAL; + } + if (!inany_v4(&new->addr) && !(fwd->caps & FWD_CAP_IPV6)) { + warn("IPv6 forward, but IPv6 not enabled"); + return -EINVAL; + } + } + if (new->proto == IPPROTO_TCP) { + if (!(fwd->caps & FWD_CAP_TCP)) { + warn("Can't add TCP forwarding rule, TCP not enabled"); + return -EINVAL; + } + } else if (new->proto == IPPROTO_UDP) { + if (!(fwd->caps & FWD_CAP_UDP)) { + warn("Can't add UDP forwarding rule, UDP not enabled"); + return -EINVAL; + } + } else { + warn("Unsupported protocol 0x%hhx (%s) for forwarding rule", + new->proto, ipproto_name(new->proto)); return -EINVAL; }

-- Stefano