Add truncate to defintions

This indicates an option might be truncated from it's natural
length and will be zero padded on expansion.
Only supported for the ip6address option.

While here, support 1 as a bitflag to just print the bit.

Fixes #508.

diff --git a/src/dhcp-common.c b/src/dhcp-common.c
index 8370addadc000b4922ce1f620fa6e4e8a1edf0fb..14d2d92a8f05d9d428aa141f3ed4a5290552e9eb 100644 (file)
--- a/src/dhcp-common.c
+++ b/src/dhcp-common.c
@@ -135,6 +135,8 @@ dhcp_print_option_encoding(const struct dhcp_opt *opt, int cols)
                printf(" request");
        if (opt->type & OT_NOREQ)
                printf(" norequest");
+       if (opt->type & OT_TRUNCATED)
+               printf(" truncated");
        putchar('\n');
        fflush(stdout);
 }
@@ -614,6 +616,8 @@ dhcp_optlen(const struct dhcp_opt *opt, size_t dl)
                return (ssize_t)dl;
        }
        if (dl < sz) {
+               if (opt->type & OT_TRUNCATED)
+                       return (ssize_t)dl;
                errno = EOVERFLOW;
                return -1;
        }
@@ -751,6 +755,11 @@ print_option(FILE *fp, const char *prefix, const struct dhcp_opt *opt,
                    l < sizeof(opt->bitflags);
                    l++, sl--)
                {
+                       if (opt->bitflags[l] == '1') {
+                               if (fprintf(fp, "%d", *data & (1 << sl)) == -1)
+                                       goto err;
+                               continue;
+                       }
                        /* Don't print NULL or 0 flags */
                        if (opt->bitflags[l] != '\0' &&
                            opt->bitflags[l] != '0' &&
@@ -808,9 +817,14 @@ print_option(FILE *fp, const char *prefix, const struct dhcp_opt *opt,
                                goto err;
                        data += sizeof(addr.s_addr);
                } else if (opt->type & OT_ADDRIPV6) {
+                       uint8_t databuf[sizeof(struct in6_addr)] = { 0 };
+                       size_t datalen = e - data >= 16 ? 16 : (size_t)(e - data);
                        char buf[INET6_ADDRSTRLEN];
 
-                       if (inet_ntop(AF_INET6, data, buf, sizeof(buf)) == NULL)
+                       /* avoid inet_ntop going beyond our option space by
+                        * copying out into a temporary buffer. */
+                       memcpy(databuf, data, datalen);
+                       if (inet_ntop(AF_INET6, databuf, buf, sizeof(buf)) == NULL)
                                goto err;
                        if (fprintf(fp, "%s", buf) == -1)
                                goto err;

diff --git a/src/dhcp-common.h b/src/dhcp-common.h
index 6a1800cf1b727086e83a0222fb62df0e047410ea..ecee7674c25036e91623cc476453f12ef77909ec 100644 (file)
--- a/src/dhcp-common.h
+++ b/src/dhcp-common.h
@@ -76,6 +76,7 @@
 #define        OT_BITFLAG              (1 << 27)
 #define        OT_RESERVED             (1 << 28)
 #define        OT_URI                  (1 << 29)
+#define        OT_TRUNCATED            (1 << 30)
 
 #define        DHC_REQ(r, n, o) \
        (has_option_mask((r), (o)) && !has_option_mask((n), (o)))

diff --git a/src/dhcpcd-definitions-small.conf b/src/dhcpcd-definitions-small.conf
index 4d39e2eb1a0b2dd5853e3f287141ad025f823f15..3e7091b0eea1d9370b5b6182a6b23c870609b33e 100644 (file)
--- a/src/dhcpcd-definitions-small.conf
+++ b/src/dhcpcd-definitions-small.conf
@@ -71,10 +71,10 @@ embed               uint32                  mtu
 
 definend 24    index embed             route_information
 embed          byte                    length
-# bits 4 and 5 are route preference, but we can't express this
-embed          byte                    reserved
+# bits 4 and 5 are route preference
+embed          bitflags=00011          prf
 embed          uint32                  lifetime
-embed          ip6address              prefix
+embed          truncated ip6address    prefix
 
 # ND6 options, RFC6101
 definend 25    index embed             rdnss

diff --git a/src/dhcpcd-definitions.conf b/src/dhcpcd-definitions.conf
index dc24533763f3dbbc5bf63953e67bb9426ef0229e..f73721148efe5f769fe2b3e643b04989efc45264 100644 (file)
--- a/src/dhcpcd-definitions.conf
+++ b/src/dhcpcd-definitions.conf
@@ -414,10 +414,10 @@ embed             uint16                  lifetime
 
 definend 24    index embed             route_information
 embed          byte                    length
-# bits 4 and 5 are route preference, but we can't express this
-embed          byte                    reserved
+# bits 4 and 5 are route preference
+embed          bitflags=00011          prf
 embed          uint32                  lifetime
-embed          ip6address              prefix
+embed          truncated ip6address    prefix
 
 # ND6 options, RFC6101
 definend 25    index embed             rdnss

diff --git a/src/dhcpcd.conf.5.in b/src/dhcpcd.conf.5.in
index 6b63c6f751e9ff1d9e015a70b0e0f29e7b52e418..179be73ee3df5b5532f504d7bf896a01674092fd 100644 (file)
--- a/src/dhcpcd.conf.5.in
+++ b/src/dhcpcd.conf.5.in
@@ -24,7 +24,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 15, 2025
+.Dd June 12, 2025
 .Dt DHCPCD.CONF 5
 .Os
 .Sh NAME
@@ -957,6 +957,10 @@ The option can appear more than once and will be indexed.
 .It Ic array
 The option data is split into a space separated array, each element being
 the same type.
+.It Ic truncated
+The option might truncated from its normal length.
+The end of the normal size is zero padded on expansion.
+Currently this is only supported for ip6address where it's a prefix.
 .El
 .Ss Types to define
 The type directly affects the length of data consumed inside the option.
@@ -979,6 +983,7 @@ C 00100000, etc.
 If the bit is not set, the flag is not printed.
 A flag of 0 is not printed even if the bit position is set.
 This is to allow reservation of the first bits while assigning the last bits.
+A flag of 1 prints the bit set or unset.
 .It Ic int16
 A signed 16bit integer, 2 bytes.
 .It Ic uint16

diff --git a/src/if-options.c b/src/if-options.c
index 1b256fa9afa17970381264632d4ba0ceaa2caaca..3cb89f35e651f4e7730d18d94cb2bb7f0571af38 100644 (file)
--- a/src/if-options.c
+++ b/src/if-options.c
@@ -1995,6 +1995,15 @@ err_sla:
                                return -1;
                        }
                        *fp++ = '\0';
+               } else if (strcasecmp(arg, "truncated") == 0) {
+                       t |= OT_TRUNCATED;
+                       arg = strskipwhite(fp);
+                       fp = strwhite(arg);
+                       if (fp == NULL) {
+                               logerrx("incomplete truncated type");
+                               return -1;
+                       }
+                       *fp++ = '\0';
                }
                if (strcasecmp(arg, "ipaddress") == 0)
                        t |= OT_ADDRIPV4;
@@ -2084,6 +2093,10 @@ err_sla:
                                t |= OT_RESERVED;
                        }
                }
+               if (t & OT_TRUNCATED && t != (OT_ADDRIPV6 | OT_TRUNCATED)) {
+                       logerrx("truncated only works for ip6address");
+                       return -1;
+               }
                if (opt != O_EMBED) {
                        for (dl = 0, ndop = *dop; dl < *dop_len; dl++, ndop++)
                        {