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Reduce the risk of change chaining transactions #2380

Merged
merged 5 commits into from Feb 22, 2019
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@@ -57,7 +57,8 @@ static struct command_result *check_amount(const struct wallet_tx *wtx,

struct command_result *wtx_select_utxos(struct wallet_tx *tx,
u32 fee_rate_per_kw,
size_t out_len)
size_t out_len,
u32 maxheight)
{
struct command_result *res;
struct amount_sat fee_estimate;
@@ -66,6 +67,7 @@ struct command_result *wtx_select_utxos(struct wallet_tx *tx,
struct amount_sat amount;
tx->utxos = wallet_select_all(tx->cmd, tx->cmd->ld->wallet,
fee_rate_per_kw, out_len,
maxheight,
&amount,
&fee_estimate);
res = check_amount(tx, amount);
@@ -88,6 +90,7 @@ struct command_result *wtx_select_utxos(struct wallet_tx *tx,
tx->utxos = wallet_select_coins(tx->cmd, tx->cmd->ld->wallet,
tx->amount,
fee_rate_per_kw, out_len,
maxheight,
&fee_estimate, &tx->change);
res = check_amount(tx, tx->amount);
if (res)
Copy path View file
@@ -29,5 +29,6 @@ struct command_result *param_wtx(struct command *cmd,

struct command_result *wtx_select_utxos(struct wallet_tx *tx,
u32 fee_rate_per_kw,
size_t out_len);
size_t out_len,
u32 maxheight);
#endif /* LIGHTNING_COMMON_WALLET_TX_H */
Copy path View file
@@ -891,7 +891,7 @@ static struct command_result *json_fund_channel(struct command *cmd,
}

res = wtx_select_utxos(&fc->wtx, *feerate_per_kw,
BITCOIN_SCRIPTPUBKEY_P2WSH_LEN);
BITCOIN_SCRIPTPUBKEY_P2WSH_LEN, 0);
if (res)
return res;

Copy path View file
@@ -711,7 +711,9 @@ static bool test_wallet_outputs(struct lightningd *ld, const tal_t *ctx)
"wallet_add_utxo with close_info");

/* Now select them */
utxos = wallet_select_coins(w, w, AMOUNT_SAT(2), 0, 21, &fee_estimate, &change_satoshis);
utxos = wallet_select_coins(w, w, AMOUNT_SAT(2), 0, 21,
0 /* no confirmations required */,
&fee_estimate, &change_satoshis);
CHECK(utxos && tal_count(utxos) == 2);

u = *utxos[1];
Copy path View file
@@ -254,6 +254,7 @@ static const struct utxo **wallet_select(const tal_t *ctx, struct wallet *w,
const u32 feerate_per_kw,
size_t outscriptlen,
bool may_have_change,
u32 maxheight,
struct amount_sat *satoshi_in,
struct amount_sat *fee_estimate)
{
@@ -283,6 +284,13 @@ static const struct utxo **wallet_select(const tal_t *ctx, struct wallet *w,
struct amount_sat needed;
struct utxo *u = tal_steal(utxos, available[i]);

/* If we require confirmations check that we have a
* confirmation height and that it is below the required
* maxheight (current_height - minconf */

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@niftynei

niftynei Feb 21, 2019

Collaborator

ubernit: missing )

if (maxheight != 0 &&
(!u->blockheight || *u->blockheight > maxheight))

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@niftynei

niftynei Feb 21, 2019

Collaborator

tbh i find maxheight not intuitive wrt to what you're checking for here. maybe something like gated_confirmation_height or req_conf_height ... neither of these seems exactly right.

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@cdecker

cdecker Feb 21, 2019

Author Member

Yeah, I've been going back and forth with the name, it's the maximum acceptable confirmation_height really, and being maybe the special value 0 is what makes it confusing.

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@rustyrussell

rustyrussell Feb 22, 2019

Contributor

Yeah, 0-as-special here is OK. Sometimes I gratuitously use a pointer so NULL can mean "don't care"...

continue;

tal_arr_expand(&utxos, u);

if (!wallet_update_output_status(
@@ -332,14 +340,15 @@ const struct utxo **wallet_select_coins(const tal_t *ctx, struct wallet *w,
struct amount_sat sat,
const u32 feerate_per_kw,
size_t outscriptlen,
u32 maxheight,
struct amount_sat *fee_estimate,
struct amount_sat *change)
{
struct amount_sat satoshi_in;
const struct utxo **utxo;

utxo = wallet_select(ctx, w, sat, feerate_per_kw,
outscriptlen, true,
outscriptlen, true, maxheight,
&satoshi_in, fee_estimate);

/* Couldn't afford it? */
@@ -353,6 +362,7 @@ const struct utxo **wallet_select_coins(const tal_t *ctx, struct wallet *w,
const struct utxo **wallet_select_all(const tal_t *ctx, struct wallet *w,
const u32 feerate_per_kw,
size_t outscriptlen,
u32 maxheight,
struct amount_sat *value,
struct amount_sat *fee_estimate)
{
@@ -361,7 +371,7 @@ const struct utxo **wallet_select_all(const tal_t *ctx, struct wallet *w,

/* Huge value, but won't overflow on addition */
utxo = wallet_select(ctx, w, AMOUNT_SAT(1ULL << 56), feerate_per_kw,
outscriptlen, false,
outscriptlen, false, maxheight,
&satoshi_in, fee_estimate);

/* Can't afford fees? */
Copy path View file
@@ -319,14 +319,16 @@ const struct utxo **wallet_select_coins(const tal_t *ctx, struct wallet *w,
struct amount_sat value,
const u32 feerate_per_kw,
size_t outscriptlen,
u32 maxheight,
struct amount_sat *fee_estimate,
struct amount_sat *change_satoshi);

const struct utxo **wallet_select_all(const tal_t *ctx, struct wallet *w,
const u32 feerate_per_kw,
size_t outscriptlen,
struct amount_sat *sat,
struct amount_sat *fee_estimate);
const u32 feerate_per_kw,
size_t outscriptlen,
u32 maxheight,
struct amount_sat *sat,
struct amount_sat *fee_estimate);

/**
* wallet_confirm_utxos - Once we've spent a set of utxos, mark them confirmed.
Copy path View file
@@ -139,7 +139,7 @@ static struct command_result *json_withdraw(struct command *cmd,
}

res = wtx_select_utxos(&withdraw->wtx, *feerate_per_kw,
tal_count(withdraw->destination));
tal_count(withdraw->destination), 0);
if (res)
return res;

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