Re: [PATCH nf-next] nft_osf: Add ttl option support

[Fernando Fernandez Mancera]

On 9/18/18 1:15 AM, Pablo Neira Ayuso wrote:

On Sun, Sep 16, 2018 at 09:10:16PM +0200, Fernando Fernandez Mancera wrote:

Add ttl option support to the nftables "osf" expression.

Signed-off-by: Fernando Fernandez Mancera <ffmanc...@riseup.net>
---
  include/linux/netfilter/nfnetlink_osf.h      |  3 ++-
  include/uapi/linux/netfilter/nf_tables.h     |  7 +++++++
  include/uapi/linux/netfilter/nfnetlink_osf.h |  1 +
  net/netfilter/nfnetlink_osf.c                |  5 +++--
  net/netfilter/nft_osf.c                      | 14 +++++++++++++-
  5 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/linux/netfilter/nfnetlink_osf.h 
b/include/linux/netfilter/nfnetlink_osf.h
index ecf7dab81e9e..c6000046c966 100644
--- a/include/linux/netfilter/nfnetlink_osf.h
+++ b/include/linux/netfilter/nfnetlink_osf.h
@@ -27,6 +27,7 @@ bool nf_osf_match(const struct sk_buff *skb, u_int8_t family,
                  const struct list_head *nf_osf_fingers);

const char *nf_osf_find(const struct sk_buff *skb,

-                        const struct list_head *nf_osf_fingers);
+                       const struct list_head *nf_osf_fingers,
+                       const int ttl_check);

#endif /* _NFOSF_H */

diff --git a/include/uapi/linux/netfilter/nf_tables.h 
b/include/uapi/linux/netfilter/nf_tables.h
index e23290ffdc77..85df36521153 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -1493,9 +1493,16 @@ enum nft_flowtable_hook_attributes {
  };
  #define NFTA_FLOWTABLE_HOOK_MAX       (__NFTA_FLOWTABLE_HOOK_MAX - 1)

+/**

+ * enum nft_osf_attributes - nftables osf expression netlink attributes
+ *
+ * @NFTA_OSF_DREG: destination register (NLA_U32: nft_registers)
+ * @NFTA_OSF_TTL: Value of the TTL osf option (NLA_U8)
+ */
  enum nft_osf_attributes {
        NFTA_OSF_UNSPEC,
        NFTA_OSF_DREG,
+       NFTA_OSF_TTL,
        __NFTA_OSF_MAX,
  };
  #define NFTA_OSF_MAX (__NFTA_OSF_MAX - 1)
diff --git a/include/uapi/linux/netfilter/nfnetlink_osf.h 
b/include/uapi/linux/netfilter/nfnetlink_osf.h
index 272bc3195f2d..7e0c00658bf8 100644
--- a/include/uapi/linux/netfilter/nfnetlink_osf.h
+++ b/include/uapi/linux/netfilter/nfnetlink_osf.h
@@ -26,6 +26,7 @@

#define NF_OSF_FLAGMASK (NF_OSF_GENRE | NF_OSF_TTL | \

                                 NF_OSF_LOG | NF_OSF_INVERT)
+

You can remove this entire patch chunk. This newline is not needed >

  /* Wildcard MSS (kind of).
   * It is used to implement a state machine for the different wildcard values
   * of the MSS and window sizes.
diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
index 00db27dfd2ff..ec8fa9661538 100644
--- a/net/netfilter/nfnetlink_osf.c
+++ b/net/netfilter/nfnetlink_osf.c
@@ -257,7 +257,8 @@ nf_osf_match(const struct sk_buff *skb, u_int8_t family,
  EXPORT_SYMBOL_GPL(nf_osf_match);

const char *nf_osf_find(const struct sk_buff *skb,

-                       const struct list_head *nf_osf_fingers)
+                       const struct list_head *nf_osf_fingers,
+                       const int ttl_check)
  {
        const struct iphdr *ip = ip_hdr(skb);
        const struct nf_osf_user_finger *f;
@@ -275,7 +276,7 @@ const char *nf_osf_find(const struct sk_buff *skb,

list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {

                f = &kf->finger;
-               if (!nf_osf_match_one(skb, f, -1, &ctx))
+               if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
                        continue;

genre = f->genre;

diff --git a/net/netfilter/nft_osf.c b/net/netfilter/nft_osf.c
index 5af74b37f423..b63c5f5c716b 100644
--- a/net/netfilter/nft_osf.c
+++ b/net/netfilter/nft_osf.c
@@ -6,10 +6,12 @@

struct nft_osf {

        enum nft_registers      dreg:8;
+       u8                      ttl;
  };

static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {

        [NFTA_OSF_DREG]         = { .type = NLA_U32 },
+       [NFTA_OSF_TTL]          = { .type = NLA_U8 },
  };

static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,

@@ -21,6 +23,7 @@ static void nft_osf_eval(const struct nft_expr *expr, struct 
nft_regs *regs,
        const struct tcphdr *tcp;
        struct tcphdr _tcph;
        const char *os_name;
+       int ttl_check;

tcp = skb_header_pointer(skb, ip_hdrlen(skb),

                                 sizeof(struct tcphdr), &_tcph);
@@ -33,7 +36,8 @@ static void nft_osf_eval(const struct nft_expr *expr, struct 
nft_regs *regs,
                return;
        }

- os_name = nf_osf_find(skb, nf_osf_fingers);

+       ttl_check = priv->ttl;
+       os_name = nf_osf_find(skb, nf_osf_fingers, ttl_check);
        if (!os_name)
                strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
        else
@@ -47,6 +51,11 @@ static int nft_osf_init(const struct nft_ctx *ctx,
        struct nft_osf *priv = nft_expr_priv(expr);
        int err;

+ if (!tb[NFTA_OSF_TTL] || nla_get_u8(tb[NFTA_OSF_TTL]) < 0 ||

+           nla_get_u8(tb[NFTA_OSF_TTL]) > 2)

Better:

         u8 ttl;

        if (!tb[NFTA_OSF_TTL]) {
                 ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
                 if (ttl > 2)
                         return -EOPNOTSUPP;
         }

+               return ~EINVAL;

                        ^
                 This is not a minus :-).

Sorry, it is a typo. I am going to fix it.

+       priv->ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
+
        priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
        err = nft_validate_register_store(ctx, priv->dreg, NULL,
                                          NFTA_DATA_VALUE, NFT_OSF_MAXGENRELEN);
@@ -60,6 +69,9 @@ static int nft_osf_dump(struct sk_buff *skb, const struct 
nft_expr *expr)
  {
        const struct nft_osf *priv = nft_expr_priv(expr);

+ if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl))

+               goto nla_put_failure;
+
        if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
                goto nla_put_failure;

--

2.18.0